Industrial prosperity is the prerequisite and foundation of rural revitalization, while rural collective operating construction land (COCL), as an important resource for rural industrial development, has significant theoretical and practical guiding significance regarding whether its market-oriented reform can promote rural industrial integration (RII). This study innovatively combines the synthetic control method (SCM) and mediation effect model to assess the impact of rural collective operating construction land entering the market (COCLEM) on RII, using panel data from 86 counties in Hunan Province (2011–2022), and its underlying mechanisms. This study finds that COCLEM significantly enhances RII, and this conclusion remains robust after a series of tests. A mechanism analysis indicates that COCLEM primarily promotes RII through population agglomeration, fiscal support, and technological upgrading. Furthermore, this study reveals that COCLEM effectively facilitates the extension of the agricultural industry chain and promotes the development of agricultural services. Nevertheless, the improvement of rural infrastructure still requires policy guidance and sustained investment to provide more robust support for RII. Therefore, policymakers should actively formulate a COCLEM policy framework, enhance rural public services, and increase infrastructure investment to continuously promote regional population agglomeration. Local governments should be responsible for ensuring policy implementation and financial support. Additionally, emphasis should be placed on the role of COCLEM in advancing agricultural technology to support RII. Compared with existing research, this study provides new empirical methods and theoretical insights for detailed research on the development of RII.