Abstract: It is urgent to ensure the quality of agricultural products, an issue increasingly drawing the public concern. The rapidly developing farmers' cooperatives play a key role in quality control (QC) of agricultural products. Based on the analysis of their effectiveness in QC, this paper explores their internal governance mechanism based on QC. It can be concluded that effective QC can be realized by the cooperatives through the reallocation of decision-making power in production, the benefit of scale economy, and the supervision mechanism with dual constraints of regulations and reputation. Meanwhile, in order to improve the efficiency and efficacy of QC, as well as to stimulate the members' cooperative efforts and eliminate the free-riding actions, the internal governance mechanism should be improved in such aspects as operational capability, governance structure, supervision mechanism, and access-exit management.