The invention relates to a method for drawing correction curve of relative efficiency of a power generator. The method is characterized in that under the windows operating system, the procedure of correction curve of relative efficiency of the power generator compiled in Fortran language is adopted, and the operation is performed under the windows operating system. The method comprises the following steps: the data required in the calculation of the power generator is input to an input document named 'in' under the master catalogue of the procedure; different hydrogen pressures and different power factors of the power generator are calculated, the copper loss of stators and the added loss of the power generator are changed with the stator current under the operating mode assigned different force output, the excitation loss is changed with the stator current, the correction percentage of the relative efficiency is calculated, and the curve of the relative efficiency of the power generator is drawn. The invention has the advantages of programming, elaboration and simple and convenient operation.