The design of Inductance–capacitor–inductance (LCL) grid-connected inverter based on linear quadratic regulation (LQR) has been studied widely, while the performance of the controller is not analyzed in these designs. In this paper, a new design method of LCL is discussed in detail. Different from the existing method parameter of the LQR controller is obtained according to the pole assignment. Besides, parameters of LCL-type filter are designed in term of the characteristics of the new closed-loop system. Further, the robustness of the system is analyzed separately. At last, various performances of the new design system are verified by simulation. The suppression ability of the system for switching harmonics is verified in the rated state and in the case of power change. The performance including better robustness and better resistance to weak grid comparison of the traditional design is also shown in this paper.