The invention relates to a calculating method for the carbon oxide emission of a generator set after the introduction of a pumped storage device. The method comprises the steps that the carbon oxide emission of the thermal generator set, the carbon oxide emission generated by the pumped storage device in the unit time in the working process, the carbon oxide emission generated when the thermal generator set is in the stable operation process after the pumped storage device is introduced into the thermal generator set, the carbon oxide emission of the thermal generator set when the pumped storage device carries out power transmission and distribution work after the pumped storage device is introduced into the thermal generator set, and the total carbon oxide emission of the thermal generator set with a traditional thermal generator facility as matched peak and valley load regulating equipment are calculated; finally, the reduced carbon emission of the thermal generator set after the pumped storage device is introduced is obtained according to a calculation result. The calculating method can provide theoretical data support for energy conservation and emission reduction.