This paper presented a single current active damping method based on two- degrees-of-freedom proportional integral derivative (2DOF-PID) control for LCL-type grid-connected inverter, which consists of proportional integral (PI) links and incomplete differential link. PI part is used to control the grid-connected current to inject the grid with high-quality. Incomplete differential part enhances the damping coefficient of LCL inverter, effectively suppresses the resonance peak caused between the inverter and the grid to improve the system reliability and stability, and speeds up the dynamic response. This method does not require additional voltage / current sensor, thus reducing the inverter cost. By establishing the transfer function of the 2DOF-PID controller, the system stability margin and dynamic characteristics were analyzed, and the proper control parameters were selected. The simulation and experiment platforms were built. The simulation and experiment results have shown that, in LCL-type grid-connected inverter under 2DOF-PID controller, the total harmonic distortion (THD) of grid-connected current is only 2.2% at full load, which is far below the national standard (GB/T 30427-2013). When the loads change from a half to all, the system overshoot reduces to 9 %, and the system response is faster than other methods.