Abstract: In recent years, lots of photovoltaic (PV) power plants have been built in China and abroad. To make full use of PV energy, the maximum power point tracking (MPPT) method is usually adopted in the existing PV systems. However, with more and more PV plants integrated into power gird, synchronous generators such as thermal, hydro units are replaced, the frequency regulation capability and inertia of power system are all in declining trend, as a result that frequency stability is difficult to guarantee in case of system emergency. Therefore, it is of important significance to make PV plants participate in system frequency regulation. A centralized frequency regulation strategy of PV plant based on equal adjustable capacity proportion mode is proposed in this paper. When the system frequency changes due to some disturbances, the measured frequency is used to calculate the shift quantity, the requirement of adjust value for active power is then got. The original active power reference is added with this adjust value to obtain the final active power reference as to change the active power output of PV units to participate in system primary frequency regulation. On this basis, in order to allow all PV units in same PV plant to coordinate with each other, also to prevent some PV units from excessive regulation, a proportional regulation of power method is implemented to allocate active power reference to each PV unit more reasonable, namely, each PV unit’s output is according to equal adjustable capacity proportion. Finally, an actual PV plant model is established on DIgSILENT PowerFactory platform to verify the effectiveness of the proposed control strategy.