First, China must invest to earn foreign exchange in US dollars through export processing. Otherwise, our dollar foreign exchange will suffer losses or assets will shrink due to the depreciation of the dollar, the interest paid by banks on foreign exchange deposits of enterprises, and the hedging cost of the central bank's implementation of the foreign exchange settlement and sale system. Therefore, buying US Treasury bonds can earn US dollar interest. Second, US Treasury bonds have high security and good liquidity, and can be realized at any time; Because its US Treasury bonds have a good credit, and the United States is a superpower, ranking first in military, science and technology, and finance, it is safest to buy US Treasury bonds, so it is impossible to buy Iraqi Treasury bonds! Third, China's domestic demand is insufficient, and people's income level is not very high. Most of the products produced by enterprises are exported. We earn dollars by exporting, and use dollars to buy US Treasury bonds. The United States has dollars to buy our products. As long as the United States continues to buy our products, our factory can be restarted, which will increase the employment rate and increase labor income. So many Americans have been borrowing money to spend, and we have money to deposit in the bank. Fourth, keeping the exchange rate stable and buying US Treasury bonds can avoid the decline of the US dollar exchange rate and the appreciation of the RMB, which is beneficial to the export of products.