The invention discloses an operation safety adaptive evaluation method for a thermal power generating unit in a primary frequency modulation performance test and belongs to the field of power system automatic control. The method comprises three evaluation submethods: unit steady-state characteristic estimation, unit dynamic characteristic estimation and unit low-frequency oscillation risk evaluation. The method guarantees that the applied disturbance amplitude for the primary frequency modulation performance test of the thermal power generating unit is limited within a safety bound of the unitaccording to the WAMS data, uploaded by a power plant through a PMU, through state comparison, model simulation, parameter identification and disturbance testing and simulation, thereby avoiding thepower oscillation, combustion instability and big vibration of the unit in a testing process, and effectively guaranteeing the power generation safety.