In order to stabilize the wind power output fluctuation, considering that the wind power and hydropower have good complementarities, this paper proposes a complementary optimal operation strategy of wind power and cascade hydropower station. In view of the wind speed uncertainty, the output of wind power can be regarded as a random variable. From the perspective of the stability and economy of wind power-hydropower complementary operation and ensuring subsequent power generation capacity, a multi-objective stochastic optimization model based on chance constraint is established. The cosine migration model, the mutation strategy of differential evolution algorithm and the dynamic non-uniform mutation operator are introduced into the improved Biogeography-Based Optimization (BBO) algorithm to solve the optimization model, and stochastic simulation technique is used to solve the chance constraint. Through time-division dynamic rolling decision based on wind power prediction and runoff forecast, the subsequent operation modes of wind power and hydropower is constantly revised to further improve reliability of complementary operation. Taking the complementary operation of a large-scale wind farm and a three-stage cascade hydropower station as an example, the feasibility and effectiveness of the proposed model, algorithm and strategy are verified. This work is supported by National Natural Science Foundation of China (No. 51277057).