As an important experimental platform for deepening reform and opening up in the new era, whether the free trade pilot zone can effectively promote the upgrading of export industries has an important impact on the high-quality development of China's trade. Therefore, the authors aim to explore whether the construction of the free trade pilot zone can effectively promote the upgrading of the export industry through the optimization of the human capital structure, and whether there are differences in the effects of the construction of the free trade pilot zone in terms of the technical level, the regional distribution of the eastern and western regions, the "city-district" distribution form and the establishment of different batches of free trade pilot zones. The authors take the construction of free trade pilot zone as a quasi-natural experiment, and use the double difference method to evaluate the impact of the construction of free trade pilot zone on the upgrading of China's export industry. The conclusions are as follows: 1) The construction of the free trade pilot zone has effectively promoted the upgrading of China's export industry, and the empirical results are still stable after carrying out strict identification assumptions and robustness tests. 2) From the perspective of impact mechanism, the free trade pilot zone promotes the upgrading of export industry through the optimization of human capital structure. 3) From the perspective of urban heterogeneity, cities with high technological level, the eastern region, "one city with multiple districts" and "long cycle" free trade pilot zones are more likely to promote the upgrading of export industries. The contribution of the article mainly includes the following aspects: At the research level, the existing research on the relationship between the free trade pilot zone and the upgrading of industrial structure has remained at the provincial level, ignoring the heterogeneity of cities in the upgrading of industrial structure. This paper, based on the panel data of 285 prefecture-level cities in China from 2007 to 2018, has more accurately and directly examined the impact of the free trade pilot zone on the upgrading of export industries. We should grasp the heterogeneity characteristics of the impact of the construction of free trade pilot zones on the upgrading of China's export industries as far as possible from the aspects of high and low technical level, regional characteristics of the east and the west, the form of "city-district" distribution and the establishment batch, and provide the basis for the country to formulate relevant differentiation policies. In terms of research methods, the dual difference method is used to identify the relationship between the free trade pilot zone and the upgrading of export industries, and factors such as the randomness of the location of the free trade pilot zone are included in the identification conditions, which can better solve the endogenous problems that may exist in the study. In terms of mechanism, the intermediary variables that affect the upgrading of export industries in the free trade pilot zone are examined from the perspective of human capital structure, and the mechanism research of the existing free trade pilot zone is expanded. In addition, it also captures the optimization of human capital structure from the perspective of labor skill level, which helps to fully understand the impact mechanism of the optimization of human capital structure to promote the upgrading of export industries. The conclusion of the article provides empirical evidence for the free trade pilot zone to further optimize the human capital structure and for China's industrial transformation and upgrading.