The invention provides a method for determining the operating cost of an electrothermal hydrogen multi-energy station system. The method comprises the following steps: S1, acquiring operating parameters of an electrolytic tank, a hydrogen cell and a waste heat boiler in an electrothermal hydrogen multi-energy station system; S2, according to the obtained parameters, calculating powers of the electrolytic tank, the hydrogen cell and the waste heat boiler respectively; and S3, establishing an objective function of a system operation cost and introducing all power values obtained by calculation into the objective function to determine the operating cost of the electrothermal hydrogen multi-energy station system. Therefore, the influence of costs of the hydrogen energy conversion process and the waste heat boiler in grid costs is taken into consideration and thus the operating cost of the grid is obtained accurately, so that resources in grid dispatching are utilized reasonably. Moreover,during the analysis process, the hydrogen energy conversion process is analyzed accurately, so that the reliable data reference is provided for the accurate analysis of grid stability.