Abstract: Under the condition of heterogeneous products and on the basis of a comparison of the impact of the introduction of the domestic and foreign products of different qualities into local enterprises on their markets, it is found that the maximum income tariff is not always greater than the best welfare tariff. The relative size of the maximum income tariff and the welfare tariff depends largely on the difference in the quality of the two products. In the Cournot competitive conditions, if the quality difference of the two products is less than 2/3, then the maximum income tariff is greater than the best welfare tariff; if not, then the maximum income tariff is less than the best welfare tariff. In addition, under the condition of heterogeneous products, the the impact of the best tariff on local enterprises can be related to the substitution degree of the two products.

Key words: heterogeneous products, maximum income tariff, best welfare tariff