Improving the technical complexity of export is of great significance to enhancing the competitiveness of China’s export trade and building a trade power. In this paper, the influence of the uncertainty of trade policy on the technical complexity of enterprises’ export is investigated by using the difference-in-differences method and the exogenous fact that China officially became a member of the World Trade Organization in 2001 as the natural experiment. It is found that the decrease of trade policy uncertainty can effectively promote the increase of technical complexity of enterprises’ export, and the high innovation success rate caused by the decrease of trade policy uncertainty plays an important indirect role in this process. In addition, the heterogeneity analysis shows that under different ownerships, the technical complexity of export of foreign-funded enterprises and private enterprises increases significantly due to the decrease in trade policy uncertainty, while the influence on state-owned enterprises is not obvious. From the perspective of different regions, the enterprises in coastal areas show a stronger effect of increasing export technology complexity, while the enterprises in inland areas have no obvious effect. From the perspective of different industries, the decrease of trade policy uncertainty has an incentive effect on the increase of export technology complexity of medium-and high-tech and low-tech industries, while it has an inhibitory effect on medium-and low-tech industries.