The electric spring (ES) can effectively improve the critical load (CL) power quality in view of the intermittent problems caused by new energy grid-connected power generation. When the grid voltage imbalance and line impedance resistance are large, there is control coupling. In this case, single-phase multi-ES cannot obtain stable voltage and frequency by traditional droop control. Therefore, it needs the droop control strategy with real-time correction of droop parameters. The second-order generalized integral generator is used to construct the virtual quadrature voltage and current signals to complete the single-phase dq rotational coordinate transformation. Then the optimized particle swarm optimization (PSO) is used to improve the droop coefficient in real time by detecting the voltage across the CL, collecting the balance information, and generating the state variable matrix. At the same time, the droop control module collects the circuit information in real time and inputs it to the PSO module to optimize the voltage deviation when each cycle is updated. The optimization result is fed back to the droop parameters for real-time update. Finally, the effectiveness of the proposed control strategy is verified by software simulation through comparing the traditional and the improved droop control strategies.