Abstract: In allusion to the extended single-machine infinite system containing double-fed induction generator (DFIG), the influence of switching in DFIG on transient angle stability of the system under asymmetric faults was analyzed. Based on impedance equivalent model of DFIG, the detailed expression of the limit clearing angle of the system containing DFIG under asymmetric fault was derived according to the equal-area criterion, meanwhile the effect of the two influencing factors, i.e. the ratio occupied by the wind power and the grid-connected position of the wind turbine, on the limit clearing angle of the system containing DFIG was taken into account, thus the effect of the two influencing factors on transient angle stability of the system was obtained and the applicability of the two influencing factors for different types of DFIG models were analyzed. A simulation model of an extended single-machine infinite system containing DFIG was established in PSD-BPA to verify the correctness of the theoretical analysis. Simulation results show that the results of the theoretical analysis are correct.