Due to the different operating characteristics of synchronous generators, the large-scale grid connection of wind power now has a new impact on the transient stability of power system. Firstly, the extended equal area criterion of traditional power system is introduced. Then the expressions that can be theoretically analyzed based on the extended equal area criterion and can reflect the mechanism of the influence of power control of doubly-fed induction generators on transient stability of power systems after fault are derived. Finally, the digital simulation verification of related examples is carried out by using DIgSILENT/PowerFactory, which lays a foundation for formulating the strategy of post-fault power control of doubly-fed induction generators in the future.