For a given import quota, when the demand increases, it will lead to higher domestic prices and more domestic production than the same import tariff; For a given import tariff, when the demand increases, it will lead to higher consumption and imports than the equivalent import quota, but it will have little impact on domestic prices and domestic production.

Import quotas are import quotas. A country specifies in advance the import quantity or amount of various commodities in a certain period. It can only be imported within the specified quantity and quota, and it is not allowed to import beyond the scope, or a licensing system is implemented.

Its main measures include: implementing foreign exchange control, collecting domestic taxes on imported goods, formulating regulations on buying domestic goods and restricting foreign goods, complicated customs procedures, complicated hygiene, safety and quality standards, packaging and decoration standards, etc.

According to the national regulations, China's customs has stipulated the items that can only be imported after identification, inspection and quarantine, and the items that need to be restricted for import and export due to the large domestic price difference. Mainly such as animals and plants and their products, household appliances and so on.

The forms of import quotas are:

Global quotas, that is, the quota applicable to any country or region in the world, is granted an indefinite quota according to the importer's application until the quota is full;

Country quotas, that is, fixed quotas allocated by countries and regions, are either levied unilaterally or determined by mutual agreement;

Importer quota, that is, a certain quota is allocated to different importers.

Some countries also combine import quotas with tariff collection, giving low tax, tax reduction or exemption treatment within quotas, and imposing higher tariffs or additional taxes on quotas, which is called tariff quotas. Tariff quota means that there is no limit on the absolute quantity of imported goods, but the imported goods within the prescribed tariff quota are given low tax, tax reduction or tax exemption for a certain period of time, and high tariffs, additional taxes or fines are imposed on the imported goods exceeding the quota.

The state applies non-quota management to mechanical and electrical products other than import quota management. Among them, the mechanical and electrical products that have been developed or imported in China and need to be accelerated are listed in the specific product catalogue and subject to public bidding.

The national electromechanical import and export office issues import certificates according to the winning results; The customs shall examine and release the goods with the import certificate. For other non-quota mechanical and electrical products, an automatic registration system shall be implemented.