It is the difficulty of county governance to strengthen the integration and cooperation of inter-departmental relationships. At present, affected by the bureaucracy and Tiao-kuai system, the fragmentation of county-level departments in China is more prominent, which is difficult to meet the comprehensive needs of grass-roots governance affairs. The work carried out focusing on the county-level center and the frequent interaction between the county-level departments provide an observation window for the study of the relationship between the departments. According to the degree of resource domination and dependence of different departments, county-level departments are divided into four types: strong resource control and strong dependence, strong resource control and weak dependence, weak resource control and strong dependence, and weak resource control and weak resource dependence. A stable departmental relationship was established among departments based on the long-term interaction of resources and power, and the superposition of different relationships eventually forms a circular "dominant - marginal" departmental relationship network. The dominant department is the strong department, and the marginal department is the weak department. It was found that there are two coordination mechanisms in departmental relationships, namely “hard coordination” mechanism and “soft coordination” mechanism, which differ greatly in the main body, resource base, means and effect of coordination. The departmental coordination mechanism effectively resolved the contradiction between the grass-roots governance system and the needs of governance affairs, and improved the adaptability of the grass-roots governance system.