Organizational coordination has been regarded as a vital factor to determine the environmental governance efficiency of local authority, while existing empirical studies mainly discuss the vertical decentralization but largely ignore the horizontal cross-departmental interaction within single government. Based on the data of 31 Chinese provinces from 2003 to 2017, this paper uses a panel vector autoregression (PVAR) approach, two-way fixed-effect models and dynamic panel regression with system generalized method of moments estimation (SYS-GMM) to investigate the environmental strategic interaction between two representative departments (finance department and environmental protection department) within local governments. The results indicate, on the whole, their environmental governance strategies show a significantly co-directional coordination. However, the cross-departmental interaction obviously varied in different periods and regions (even showed as conflict sometimes), and was synchronized with the dynamic trade-off between economic and environmental targets of China. This research helps understand the inner logic of environmental governance of Chinese government, and can be valuable guidance for other countries to accomplish multi-departmental sustainable development goal.