Abstract: Since China′s accession to the WTO, China′s opening up has changed from the stage of adapting to and following the international trade regulations to the stage of overall opening up and leading the trend. Based on the background of China′s gradual opening up, this paper takes the patent data of China′s A-share listed companies in 2001-2016 as the research sample, and studies the phased characteristics of the impact of trade liberalization on enterprise innovation on the basis of considering the industrial interconnection.The results show that: the impact of trade liberalization on enterprise innovation has significant stage characteristics,specifically, in the transitional stage of China′s accession to WTO, trade liberalization in this industry and upstream industry respectively have inhibition and promotion effects on enterprise innovation, while trade liberalization in downstream industry has significant inhibition effects;in the stage of all-round opening up, trade liberalization in this industry has a significant inhibiting effect on enterprise innovation, while trade liberalization in upstream and downstream industries has a significant promoting effect on enterprise innovation,that is to say, the trade liberalization of this industry will always restrain the innovation of enterprises, the trade liberalization of upstream industry will promote the innovation of enterprises, and the influence of trade liberalization of downstream industry on the innovation of enterprises presents the “U-shaped” feature of first restraining and then promoting.This shows that the relationship between trade liberalization and enterprise innovation is not immutable, but closely related to the stage of opening up and the pattern of economic competition at home and abroad. Therefore, trade policies should be adjusted in a timely and targeted manner.

Key words: trade liberalization, heterogeneous firms, industrial linkage, innovation, periodic characteristics