Compared to traditional inverter, Z source inverter has been widely used because of its advantages such as the boost and buck capability, no need to insert the dead-time and so on. Aiming at the disadvantage of high harmonic contents of output voltage and current, the LCL filter is proposed to filter, its performance is excellent, but the resonance peak is easy to cause the system instability. So in this paper the active damping scheme with inner loop of capacitor current and outer loop of grid current is adopted to suppress the resonance peak. In order to avoid tuning parameters repeatedly, a control parameter design method is proposed, which is the pole assignment of the transfer function, so as to obtain the optimal control parameters. Under the premise of ensuring the stability of system, the system has better robustness. Finally, the effectiveness and feasibility of the proposed scheme are verified by simulation and experimental results. This work is supported by National Natural Science Foundation of China (No. 61203224) and Natural Science Foundation of Shanghai (No. 13ZR1417800).