As a policy experiment of China''s deepening reform and opening up, the pilot free trade zone attempts to realize the liberalization and facilitation of trade and investment through institutional innovation. What is the policy effect? Based on the panel data of 216 prefecture-level cities from 2000 to 2019, the influence of China''s pilot free trade zone on foreign direct investment was tested by generalized synthetic control method. It is found that: the pilot free trade zone has attracted foreign direct investment to a certain extent, and its positive role in promoting foreign direct investment has become increasingly obvious over time. The results of multi-period difference in difference method for controlling other policy factors further verify the reliability of the above conclusions. Further research finds that there are differences in the policy effects of the pilot free trade zone to foreign direct investment. From the time trend, the policy orientation of different batches of the pilot free trade zone is different, and the impact on foreign direct investment is different. From the regional perspective, in the construction of the pilot free trade zone, the eastern region has a stronger role in promoting foreign direct investment, the policy effect in the central region has a lag, and the western region has a downward trend in attracting foreign direct investment. From the perspective of city size, the attraction of the pilot free trade zone to foreign direct investment in first-tier cities is more obvious. The lower the city level is, the stronger the plasticity of cities is, and the more significant the effect of attracting foreign direct investment is. From different development gradients, the positive impact of the coastal pilot free trade zone on foreign direct investment is higher than that of the inland pilot free trade zone, while the border pilot free trade zone does not show the attraction to foreign direct investment.