To more effectively cooperation response of adjustable resources within the integrated energy system, a two-layer optimization method based on chance constraints for integrated demand response (IDR) in industrial parks is proposed. Firstly, based on the integrated energy system framework of the industrial park, an incentive-based integrated demand response strategy is developed, along with an interactive response framework involving the industrial park operator, load aggregator and the main grid. Then, to address the uncertainty in load response, the chance constraint method is introduced,and coordinated response strategy between air-conditioning and aluminum electrolysis load is proposed to improve response reliability. Finally, a two-layer optimization method is established, with the industrial park operator as the upper layer and the load aggregator as the lower layer. The model is solved using a hybrid approach that embeds the Gurobi solver within a particle swarm optimization algorithm. The simulation results show that the proposed two-layer optimization method can achieve a coordinated response of energy conversion equipment and multiple loads. It reduces the response cost of the industrial park and improves the reliability and economic efficiency of integrated demand response.