Considering prediction accuracy of wind and solar power generation increasing with time scale reduction, a multi-time scale unit commitment model with wind and solar power output rotating reserve capacity is established. Meanwhile, dispatching method considering uncertainty of wind and solar power is established. Based on three time scales reduced step by step, the model updates predicted values of wind and solar power step by step to the equivalent load of wind and solar power output and rotating reserve. Then, the lower level is used to correct the upper level deviation, and the dynamic programming algorithm is used to solve the problem at different time scales to obtain the unit combination mode which approximates to maximize wind and solar output and takes economic optimization of traditional units into account. The modified IEEE 30-bus system is used as an example for simulation calculation and the results verify the validity and rationality of the proposed method.