Abstract: In order to improve the utilization rate of water energy and solve the load distribution problem of small hydropower units with optimal efficiency as the objective,a set of load optimization allocation platform for small hydropower units based on big data technology is developed. Through the analysis of basic data and online measurement data,the platform can automatically identify the state conditions,operation conditions and stability performance of the unit. On this basis,an on-line iterative efficiency surface fitting method based on real-time dynamic self-tuning is proposed to solve the problem of efficiency fitting error caused by big data sample error noise and the error caused by efficiency change after unit operation state changes,and realizes automatic real-time dynamic rendering of online efficiency surface. This paper presents an optimal active power distribution method for small hydropower units based on the comprehensive stability index and critical vibration region. The method solves the problem of safe and stable operation of the unit when the unit is under the optimal active power distribution load,and realizes the coordinated control of multiple units according to the optimal efficiency. Finally,energy saving and efficiency increase of small hydropower units are realized. It is proved that the technology is feasible by practical application.