Abstract: When the power system is disturbed, the rotor-side converter of the DFIGs will have SSCI with the capacitor of the series compensation device, which will make the DFIGs behave as a source of sub-synchronous oscillation to a certain extent, which will seriously affect to the stability of the power system. Aiming at the actual situation of DFIGs in the northwestern region of China, the occurrence mechanism of sub-synchronous oscillation is analyzed, and the electromagnetic transient model is built to study the sub-synchronous oscillation of the DFIGs on the PSCAD/EMTDC platform. A filter is added to the rotor-side converter to suppress the SSCI. Finally, the effectiveness of the suppression method is verified by comparing the time-domain simulation diagram of the output power of the DFIGs with or without the filter under the same operating conditions.