Wind power has become the focus of new energy generation by its abundant resources and clean and environmentally friendly features. However, as the proportion of wind power connected to the grid rises, there is a risk of causing sub-synchronous oscillation. For the problem of sub-synchronous oscillation, an additional damping control strategy taking into account the rotor side converter of the wind turbine was proposed. This paper establishes the wind power grid connection model, including wind turbine, MMC, and transmission line, and analyzes the generation mechanism of sub-synchronous oscillation using the impedance modeling method. The simulation test was carried out by MATLAB/Simulink. The results show that the control strategy can suppress the oscillation faster, improve the power quality better, and verify the correctness of the method.