The lithium battery energy storage system by the traditional PQ control is affected by the DC decoupling component, resulting in power quality and dynamic power compensation performance be affected, and more complex control structure. This paper adopts the grid-connected power control strategy of lithium battery energy storage based on quasi-PR controller. This strategy simplifies the traditional PQ control algorithm and eliminates the need to introduce decoupling components into the control inner loop, eliminating the use of PLL and avoiding the influence of the DC decoupling component of the control system, achieves the zero stady-state error tracking of AC, improves the power quality and response speed of grid-connected. A new tuning method is proposed to design the quasi PR controller to ensure the stability and reliability of the control system.Finally, the improved lithium battery energy storage grid-connected system simulation model is constructed to verify the feasibility and effectiveness of the designed controller.