According to heterogeneous firm trade model, if the export drawback rate is lower, the general trade and the number of the processing firms as well as export quantity will decrease, furthermore, the general trade decreases sharply. On January first, 2004, China decreases export drawback rate of partial mechanical and electrical products, which is regarded as external policy shock, the empirical test is conducted by difference in difference method, the results show that the decrease of export tax drawback obviously decrease the number of export products, this kind of inhibition effect more significantly affects the exports of general trade while has small effect on exports of feed processing trade and processing trade, that the regulation of export tax rebates on exports is implemented mainly through the impact on the intensive margin of general trade, that after the decrease of export tax rebate rate, the general trade export volume of private enterprises, trade intermediaries and inefficient enterprises is significantly affected, that after the reduction of export tax rebate rate, the export prices of the general trade enterprises rise and the export value declines. China should plannedly and rationally determine the products scope and drawback rate for export drawback, use different export drawback policy for different trade methods of the enterprises and take more neutral export drawback policy.