The LCL filter owned superior filter performance, integrated and encapsulated easily, is becoming more and more widely used in the distributed generation system connected-grid. However, the resonance occurred by zero damping not only affects the stability of the closed-loop system, but also decreases the performance of net current. So how to design and optimize the filter parameters to improve the filter performance of the filter becomes the hot spot of the research. Under the conditions of the total inductance and the capacitance can meet the filter performances, the paper analyzes comparatively how the inductance distribution coefficient and damping resistance impact on the stability of the system, filtering effect, switch order harmonic attenuation ratio, damping value and the damping loss. On this basis, proposed an optimization method, and given the general design flow chart. The simulation results show the optimization method is effective.