The invention discloses a method for judging the primary frequency modulation effect of a generator set, and the method comprises the steps: collecting PMU data and a frequency change curve graph of the generator set in a preset time period; obtaining a theoretical difference adjustment coefficient according to the type of the generator set, wherein the PMU data comprises frequency data and powerdata; obtaining an actual difference adjustment coefficient according to the PMU data and the frequency change curve graph; and comparing the actual difference adjustment coefficient with the theoretical difference adjustment coefficient, and if the actual difference adjustment coefficient is larger than the theoretical difference adjustment coefficient, determining that the frequency modulation response of the generator set is unqualified. By adopting the method, whether the primary frequency modulation effect of the generator set is qualified or not can be judged, and the reason why the generator set is unqualified can also be judged.