Abstract: The closure of open diversion channel of Jinsha Hydropower Station is faced with the problems of large flow rate, high flow rate at the gap, large drop, steep bank slope of the open channel, smooth bottom of the channel, which makes it difficult to stabilize the accumulation of throwing materials, difficult closure construction and low construction efficiency. Through the physical model test of closure, the hydraulic parameters were reasonably determined, the closure materials and dike layout were optimized to reduce the closure velocity in the open diversion channel. According to the field situation and model test results, it was proposed to in advance imbedded I-steel in the bottom of the open channel, anchor hook in the side wall of the open channel, and to in advance construct pier head dike near the smooth side of longitudinal cofferdam concrete, so as to increase the friction resistance of the flow section and improve the stability of projecting material. At the same time, a barrier gap near the longitudinal cofferdam was constructed to improve the diversion conditions, and technical measures such as controlling discharge and adopting embankment head collapse were taken to reduce difficulty and improve efficiency of closure construction. The successful application of the above measures in the engineering implementation ensured the implementation of open diversion channel closure, which can provide some reference for similar projects.