LCL output filter has been widely used in the grid-connected inverter owing to its good high-frequency harmonic attenuation performance. However, the impedance characteristic of the LCL filter has a resonance peak, which tends to cause unstable control of the grid-connected inverter. In order to effectively suppress the resonance, the inverter-side current feedback is introduced as the active damping and the mathematical model of the LCL-filtered inverter under feedback control is obtained. Since the filter parameters and control parameters are coupled to each other, the design for optimizing the filter performance while meeting the demand of control performance becomes particularly complicated. This paper puts forward an overall design method of optimizing the filter parameters and control parameters based on the particle swarm optimization algorithm. The output characteristics of the main harmonics are taken as the optimization goal in the optimal design, with consideration of the filtering performance and control performance. The simulation results verify the feasibility and effectiveness of the proposed method.