Abstract: At present, for the calculation of AGC regulating ability of photovoltaic power stations, the method based on the inverter model machine is generally adopted, without considering the actual operation status of the inverter. In view of the shortcomings of the existing technical fields and systems, this paper proposes a method for calculating the AGC regulating ability of photovoltaic power stations based on state assessment. By collecting the data of the inverter, prediction system, real-time weather and other data in the station, and based on the comprehensive analysis of big data, the real-time operation status of each inverter in the photovoltaic station is obtained. Based on the real-time operation status and preset rules, select the inverter that can be included in the AGC regulating ability calculation, and calculate and check the AGC regulating ability of the photovoltaic power station according to the screening results. The AGC regulating ability value calculated by the algorithm proposed in this paper can not be affected by the different generation capacity of different units in the photovoltaic station and the different operation status of each inverter. It provides the grid operation and dispatching department with accurate data of the AGC regulating ability of the photo-voltaic station, greatly improving the grid's perception and absorption capacity of new energy.