Abstract: In view of the characteristics of new energy, such as weak inertia, large output fluctuation and poor reactive power support capacity, which seriously affect the transient stability characteristics and the safe and stable operation of the sending end power grid with weak synchronous support, this paper uses PSASP (power system analysis software package) analysis tool and takes the sending end power grid of Xilinhot UHV AC/DC transmission project as the research object, the model of typical wind and thermal power bundled AC/DC hybrid external transmission system is built, the interaction between AC/DC system and wind-thermal power supply and the analysis method of system transient stability after large-scale wind power centralized access are deeply studied, and the transient stability of the system under AC short-circuit fault and DC bipolar locking under different proportion of wind turbine power is simulated and analyzed. It is concluded that the increase of the proportion of wind turbines power will greatly reduce the transient acceleration energy injected into the system and improve the transient power angle stability of the system, which plays a guiding role in reasonably arranging the operation mode of power grid and promoting the consumption of clean energy.