The invention discloses a substitutable degree-of-freedom index calculation method for a comprehensive energy system. The total demands of different types of loads of electricity, gas, heat and cold in the comprehensive energy system are collected, and the maximum available power of different types of energy flows of electric energy, natural gas and heat energy for a certain type of load and the maximum consumed power of the type of load are calculated. On the basis, substitutable indexes of different types of loads and substitutable degree-of-freedom indexes of the whole comprehensive energysystem are defined, and evaluation standards are provided for the substitutable degree-of-freedom of the loads in the comprehensive energy system during energy selection.