Abstract: To address the issues of inertia and frequency instability in power systems with high-penetration renewable energy, an adaptive active power droop control strategy based on equivalent active power droop is proposed for grid-forming energy storage system(GF-ESS) control. A dynamic coupling model is established for energy storage units regulated by virtual synchronous generator(VSG) technology and real synchronous generators(SGs). Analytical expressions are derived to characterize the relationship between the amplitude of frequency fluctuation(Δf) and the output active power variation(ΔP) of the energy storage unit. These expressions reveal the mechanism behind the mismatch between inertia support and power regulation caused by traditional fixed droop coefficients. Subsequently, an adaptive droop coefficient adjustment method is proposed, which dynamically modifies parameters based on real-time inertia estimation. The proposed method enables the frequency overshoot to be reduced by 0.05 Hz under continuous load changes and confines the frequency fluctuations strictly within the bandwidth of ±0.15 Hz under step load disturbances. Simulation results are presented to validate the effectiveness of the proposed method. The results show that within the coordinated frequency regulation system, the maximum deviation between the actual and theoretical output active power of the energy storage unit is less than 3%, and the deviation during the dynamic frequency response process is below 1%. This verifies the effectiveness and engineering applicability of the proposed control strategy.