Flush gallery is a common structure of hydropower station. For flush galleries with bending shape and complex structure and flow pattern, the formula to effectively calculate the flow discharge capacity is seldom seen. Based on hydraulic model test data of the first part of Nanpanjiang Bridge Hydropower Station and the energy equation, we analyzed the loss of resistance per unit flow, and thus obtained the formula for the discharge capacity of the flush gallery. The calculation results conform well with physical model test results. This research  serves as a reference for similar projects, and provides a new idea to analyze the discharge capacity of such complex structures.             