The present invention discloses a plant load optimization setting method in leading phase operation of a generator based on a PSASP. The method comprises the following steps: (1) establishing a plant load model in a basic database in the PSASP text supporting environment; (2) selecting an appropriate power grid data group, and setting part of the power plant output situation in the plant load model according to the system boot mode in a corresponding period and actual power consumption in each region; (3) carrying out power flow calculation and transient stability calculation so as to obtain the depth of phase limit of the generator under the certain working condition; and (4) by reference to that the depth of the phase of the generator under different active outputs needs to be tested when carrying out phase experiment on the actual generator, setting 3-4 working conditions of different active outputs, and carrying out calculation in the step (3) under each condition. According to the method disclosed by the present invention, existing measured data resources can be fully used, the real situation that the plant load in the high-precision simulation of actual leading phase operation in the PSASP changes with the change of the active outputs of the generator is meaningful to the power grid planning.