A multi-timescale optimal scheduling strategy for integrated energy system considering source-load uncertainty and user demand response is proposed to address the problems of source-load uncertainty and equipment power fluctuation in the energy system. First, according to the respective characteristics of the source and load, the robust optimization method and the stochastic optimization method are used to deal with the uncertainty of the source and load. Second, based on the scheduling characteristics and response differences of electricity, heat and gas loads in different time scales, a demand response model corresponding to different time scales is designed, and a multi-timescale optimization model is developed for the day-ahead and intraday phases, with the day-ahead scheduling objective of minimizing the cost of purchasing energy, the system operating cost, and the cost of carbon emission, and the intraday scheduling phase further considers the penalty of equipment regulation and the reduction of subsidy demand response costs. Finally, the model and methodology are validated through examples, and under the consideration of source-load uncertainty and demand response, the proposed methodology is able to take advantage of the complementary advantages of multiple energy sources, effectively promote the balance of energy supply and demand, and reduce the impact of source-load uncertainty on the integrated energy system.