The invention provides a water diversion type small hydropower station with a fish passing function. The water diversion type small hydropower station comprises a dam. A water diversion canal is arranged on one side of the dam. One end of the water diversion canal is provided with a water diversion inlet also serving as a fish passing channel outlet. The other end of the water diversion canal is provided with a fish blocking corral. The side, adjacent to the dam, of the water diversion canal is provided with a branch fish slope. The fish slope communicates with the water diversion canal and islocated on one side of the fish blocking corral. A plurality of evenly distributed gravel-cobbles are arranged in the fish slope transversely. The existing water diversion canal of the water diversion type small hydropower station is transformed properly and is converted into the fish passing channel in virtue of power generation, the problems that fish passing facilities in construction of the small hydropower station are too high in cost, and the small hydropower station blocks fishes and generates a large ecological influence, thereby being dismantled are avoided, no significant influenceis generated on power generation benefits, and significance is achieved for ecological transformation and upgrading of the small hydropower station and for disorderly development remediation of the small hydropower station.