Abstract: Since China’s reform and opening up, development zones (DZs) has achieved remarkable results in promoting the growth of total economic volume. Under the background of transformation and efficiency enhancement, the realization of an economic growth model supported by total factor productivity (TFP) is an inevitable trend for the development of DZs. Improving the TFP of in zone firms has also become the basic way for DZs to achieve high quality economic development. Based on the perspective of TFP, the article uses micro-firm data to study the agglomeration status and productivity levels of firms in the development zone of Nanjing and Suzhou, and analyzes its heterogeneity. Research indicates: (1）Firm agglomeration and industrial clusters have formed in DZs of the two cities. The characteristics of firms gathering in DZs are obvious, and its agglomeration situation is increasingly strengthened. Industrial agglomeration in DZs already has a considerable scale; （2)In zone firms have certain productivity advantages. Advantages of DZs are mainly reflected in the small number of low efficiency firms and the increase of the number of high efficiency firms. In addition, there are differences in productivity levels between zones and in zone firms with different characteristics. The research aims to provide scientific reference for improving the productivity of in zone firms and promoting the transformation and upgrading and sustainable development of DZs.