Using Chinese import and export data and manufacturing industry data from 2000-2021, this paper constructs indicators of the level of services liberalization and empirically examines the effects and mechanisms of services liberalization on employment size and employment structure in different manufacturing industries using Bartik instrumental variables, PSM-DID, and other methods. The study shows that, firstly, service sector opening significantly contributes to the increase of employment scale in manufacturing industry, but in terms of employment structure, service sector opening generates employment creation effect on labor-intensive industries while generating employment destruction effect on capital-intensive industries, thus causing the phenomenon of employment polarization in manufacturing industry; secondly, service sector opening enhances the employment scale in manufacturing industry through two effects of technology spillover and cost saving, and it is Second, the opening up of the service sector increases the employment scale of the manufacturing industry through two effects: technology spillover and cost saving, and it is the difference in the mechanism of these two effects in different manufacturing industries that causes the employment polarization. The conclusions have certain policy implications for maintaining the basic stability of the share of manufacturing, promoting the integration of the two sectors and accelerating the construction of a new development pattern.