The doubly-fed induction generator (DFIG), accounting for a large proportion in wind farms, due to the different operating characteristics of synchronous generators, resulting in that the large-scale access of wind power has a new impact on the transient stability of power system. Firstly, the extended equal area criterion (EEAC) of traditional power system is introduced. Then, the expressions that can be theoretically analyzed based on the EEAC and can reflect the influence mechanism of power control of DFIG on transient stability of power systems after fault are derived. Finally, the digital simulation verification of related examples is carried out through using DIg SILENT/Power Factory, which lays a foundation for formulating the fault ride-through power control strategy of wind turbine generators in the future.