To mitigate the system frequency fluctuations induced by the integration of a large amount of renewable energy sources into the grid, a novel ESS participation strategy for primary frequency regulation considering the State of Charge (SOC) is proposed. This strategy integrates virtual inertia control and virtual droop control based on the analysis of frequency deviation variation curves and their distinct control characteristics during different frequency deviation stages. Additionally, a fuzzy control-based coordination factor is introduced to harmonize the allocation of output proportions between these two control modes. Furthermore, the SOC is partitioned to establish relationships between different SOC levels and droop coefficients, enabling adjustments of the output magnitudes of the two control modes by varying the droop coefficients to prevent overcharging or over-discharging of the energy storage system (ESS). Within the deadband of frequency regulation, SOC restoration is conducted to mitigate the degradation of the ESS’s frequency regulation capability caused by excessively low or high SOC levels. Finally, a simulation platform is developed to construct a SOC-based ESS primary frequency regulation simulation model, demonstrating the effectiveness of the control strategy under step and continuous load disturbance scenarios. The abstract should summarize the contents of the paper in short term.