Abstract: The second harmonic current in the DC link of single-phase quasi-Z-source inverter（qZSI） seriously affects the performance of the system and limits its application. Aiming at suppressing the second harmonic current at the DC side of single-phase qZSI, a new strategy based on virtual impedance is proposed. The control strategy increases the closed-loop output impedance of single-phase qZSI at 2f₀ by introducing an additional control process of the serial virtual impedance to effectively reduce the second harmonic current contents at the DC side. At the same time, a closed-loop parameter design method of the control strategy is proposed considering the constraints of the second harmonic current suppression requirement and the stability margin of the system. Finally, the correctness of the second harmonic current suppression strategy and its closed-loop parameter design method proposed in this paper are verified by digital simulation and RT-LAB based hardware-in-the-loop simulation.