Aiming at the problem of serious abandonment of wind and high carbon dioxide emission in the current power system，a lowcarbon economic dispatching model for a combined electricitygas integrated energy system with power to gas(P2G) is proposed. The paper introduces the economic conversion coefficient to convert carbon dioxide emission into economic dimension and counts them in the objective function. The objective function is to minimize the sum of carbon dioxide emission cost and system operating cost while the energy flow model and safety constraints of electric power system containing powertogas and natural gas system are considered. The following optimization is realized by using the interior point method(IPOPT). The modified IEEE 30 node power system and Belgium 20 node natural gas network are used for example analysis. By comparing the comprehensive cost and carbon dioxide emissions under four different models, it is verified that the proposed model can effectively balance the low carbon and economy of the system operation, and greatly improves the ability to absorb wind power. When different economic conversion coefficients are taken, the optimal scheduling results with different emphasis on low carbon and economy are obtained.