The invention discloses a method for increasing primary frequency modulation correct action qualified rate of a thermal power generation machine set. (1) when the rotating speed signal received by a DEH rotational speed module of the thermal power generation machine set is less than 2998 rpm and DEH primary frequency modulation instructions are increased, the DEH primary frequency modulation instructions are acted in advance or in a lagged manner, so that the primary frequency modulation function effect is strengthened and negative effects on the primary frequency modulation effect due to load fluctuation per se are eliminated; when the rotating speed signal received by the DEH rotational speed module of the thermal power generation machine set is less than 2998 rpm and the DEH primary frequency modulation instructions are decreased, the DEH primary frequency modulation instructions are not corrected; (2) when the rotating speed signal received by the DEH rotational speed module of the thermal power generation machine set is greater than 3002 rpm and the DEH primary frequency modulation instructions are decreased, the DEH primary frequency modulation instructions are acted in advance or in a lagged manner, so that the primary frequency modulation function effect is strengthened and negative effects on the primary frequency modulation effect due to the load fluctuation per se are eliminated; when the rotating speed signal received by the DEH rotational speed module of the thermal power generation machine set is greater than 3002 rpm and the DEH primary frequency modulation instructions are increased, the DEH primary frequency modulation instructions are not corrected.