The theory of technical barriers regards technology as the third factor of production independent of labor and capital, and discusses the influence of technological gap or technological change on international trade. Because technological change contains time factors, the technology gap theory is regarded as a dynamic expansion of H-O theory. Because technological change contains time factors, the technology gap theory is regarded as a dynamic expansion of H-O theory. The technology gap theory came into being in 196 1, and the representative figure is American scholar M.V.Posner, who put forward the technology gap model of international trade in his article International Trade and Technological Change. The technology gap theory came into being in 196 1, and the representative figure is American scholar M.V.Posner, who put forward the technology gap model of international trade in his article International Trade and Technological Change. According to this theory, technology is actually a factor of production, and the actual level of science and technology has been improving, but the development level of different countries is different. This technology gap can make technologically advanced countries have technological comparative advantages, thus exporting technology-intensive products. According to this theory, technology is actually a factor of production, and the actual level of science and technology has been improving, but the development level of different countries is different. This technology gap can make technologically advanced countries have technological comparative advantages, thus exporting technology-intensive products. With the imitation of technology by importing countries, this comparative advantage disappears and the resulting trade ends. With the imitation of technology by importing countries, this comparative advantage disappears and the resulting trade ends. According to the technology gap theory, a large part of industrial trade between industrialized countries is actually based on the existence of technology gap. According to the technology gap theory, a large part of industrial trade between industrialized countries is actually based on the existence of technology gap. Introduce the concept of imitation lag to explain the possibility of trade between countries. The concept of imitation lag is used to explain the possibility of trade between countries. In the two-country model of innovation country and imitation country, after a new product of innovation country is successful, it has technological advantages before imitation country masters this technology, and it can export this technologically advanced product to imitation country. In the two-country model of innovation country and imitation country, after a new product of innovation country is successful, it has technological advantages before imitation country masters this technology, and it can export this technologically advanced product to imitation country. With the development of patent transfer, technical cooperation, foreign investment or international trade, the leading technology of innovative countries has spread abroad, and imitation countries have begun to use their low labor costs to produce such goods themselves and reduce imports. With the development of patent transfer, technical cooperation, foreign investment or international trade, the leading technology of innovative countries has spread abroad, and imitation countries have begun to use their low labor costs to produce such goods themselves and reduce imports. Innovative countries gradually lose the export market of this product, the international trade volume caused by the technology gap gradually shrinks, and finally it is mastered by imitation countries, and the technology gap disappears, and the trade based on the technology gap also disappears. Innovative countries gradually lose the export market of this product, the international trade volume caused by the technology gap gradually shrinks, and finally it is mastered by imitation countries, and the technology gap disappears, and the trade based on the technology gap also disappears. In 1963, GordonDouglas uses the concept of imitation time lag to explain the export mode of American film industry. That is to say, once a country is in a leading position in a particular product, it will continue to maintain this leading position in related products. In 1966, G. Hefbauer explained the trade pattern of synthetic materials industry with the concept of imitation time delay. It can be explained by the country's imitation time lag and market size. That is, the share of a country in the export market of synthetic materials. When he ranked countries according to imitation time lag, he found that countries with short imitation time lag recently introduced new synthetic material technology and began to produce and imitate countries with long imitation time lag for export. With the spread of technology, countries with long imitation time lag gradually began to produce this synthetic material, and gradually replaced the export status of countries with short imitation time lag. The empirical study of technology gap theory supports the view of technology gap theory, that is, technology is the most important factor to explain the national trade model. Foreign trade is the core of foreign economic relations of all countries in the world, an important means to accelerate the economic development of all countries, and plays an irreplaceable role in the economic development of all countries. Since the reform and opening up, foreign trade has been the "propeller" of China's economic development, and the import and export has also changed from the original deficit to a surplus. Abundant foreign exchange reserves have become a "reassurance" for the healthy development of China's economy and society. Of course, with the large trade surplus, it has also brought some new problems and attracted the attention of relevant parties. Customs statistics is an important part of national economic statistics. It is accumulated, reviewed and counted from import and export declarations, and its accuracy and authority are internationally recognized. Through the comparative analysis of customs statistics, we can have a clearer understanding of China's foreign trade development and trade surplus.