With the development of the energy Internet, integrated natural-gas and electricity energy systems have become an important form of the future energy utilization. Power-to-Gas (P2G) technique provides an alternative solution for renewable energy accommodation. Given this background,the paper presents an optimal dispatch model for integrated energy systems with P2G devices. The model considers multi-objectives, including minimum operation cost, lowest environmental pollution and wind curtailment cost. The multi-objective particle swarm algorithm is used to solve the problem, in which fuzzy theory is applied to choose the best solution with the largest comprehensive satisfaction. Numerical results verify the effectiveness of proposed model and the positive role of P2G in renewable energy accommodation. The results also indicate the changes of natural-gas load will impact the scheduling of power system, and further influence the system operation cost and environmental pollution.