["Review of Development Economics, EarlyView. ", "\nABSTRACT\nThis study examines the impact of China's commercial system reform on migration, employing a staggered difference‐in‐differences model validated by the Goodman‐Bacon decomposition using panel data from 264 prefecture‐level cities (2011–2018). The reform, characterized by market access liberalization and reduced government intervention, significantly boosted local population inflow, with an estimated average increase of 80,000 people per city per year (approximately 1.86% of the average permanent population of the sample cities). The effect was substantially larger in coastal cities and those with higher human capital stocks or large‐scale mobile populations. The mechanism involves creating more employment opportunities by facilitating enterprise entry, thus attracting people. The study also highlights urban heterogeneity, showing that coastal cities (about 169,000 population inflow, 3.94% of the average city population), those with higher human capital (about 168,000 population inflow, 3.92% of the average city population), and larger mobile populations (about 125,000 population inflow, 2.92% of the average city population) benefit more from the reform. It underscores the crucial role of commercial system reform in enhancing population inflow and provides recommendations for further enhancement.\n"]