Using county-level business registration data from China between 2009 and 2023, this study matches the actual boundaries of Pilot Free Trade Zones (PFTZs) to county-level administrative units and estimates their effects on new firm entry using group-time average treatment effects. PFTZ establishment increases new firm entry by approximately 16.1 percent. The effect emerges gradually and remains positive in most post-treatment periods, although it does not increase monotonically. Positive effects are more pronounced for the 2015–2018 cohorts, while those for the 2019 and 2020 cohorts remain statistically unstable within the available observation period. The policy promotes entry across geographic regions, with relatively larger point estimates in non-old-industrial-base, nonresource- dependent, and ecologically oriented counties. Exploratory industry-level evidence suggests stronger responses in industries sensitive to administrative licensing, investment approval, and specialized institutional services. The findings remain robust to alternative comparison groups, sample restrictions, synthetic difference-in-differences estimation, and placebo tests. These findings suggest that institutional opening-up reforms implemented through China’s Pilot Free Trade Zones can stimulate market entry, while their effects depend on local economic conditions and industry-specific entry constraints.