The influence of wind-photovoltaic hybrid farm’s intergration on the sub-synchronous oscillation of power system is studied in this paper. Firstly, the mathematical model of power system connected with wind-photovoltaic hybrid farm is established. And the trajectory of main oscillation mode change when the parameters change in wind-photovoltaic hybrid farm combined with the benchmark, these parameters are wind speed, intensity of illumination, output active power, wind/photovoltaic power ratio, DC/DC inverter MPPT control parameter, inner ring control parameter of d and q axis currents of converter at grid side, inductance of filter lines, phase-locked loop control parameter and etc. It is found that wind-photovoltaic hybrid farm’s intergration almost does not affect the sub-synchronous oscillation modes associated with synchronous generators’ shafting. However, the variation of wind-photovoltaic hybrid farm’s parameters may lead to the instability of the sub-synchronous oscillation mode associated with the wind-photovoltaic hybrid farm. Sub-synchronous damping controller attached to the grid-side converter of wind-photovoltaic hybrid farm can improve the damping of power system and suppress the sub-synchronous oscillation. And the results of modal analysis and nonlinear simulation verify the effectiveness of the sub-synchronous damping controller.