Abstract: The large-scale wind power convergence area has few supporting thermal power units,which belongs to AC weak power grid,and the transient overvoltage problem after fault is serious. Since 2011,dozens of wind power transient overvoltage disconnection events have occurred in northwest,and northeast,worth China and other regional power grids. In the accidents,the proportion of wind turbines off grid caused by fault recovery overvoltage is very high,and the degree of overvoltage directly affects the starting capacity of wind farms. In order to solve this problem,a grid connected model of permanent magnet synchronous generator（PMSG）is established based on typical low voltage ride through（LVRT）strategy,and the influencing factors of transient overvoltage at PMSG terminal at the time of clearing short circuit fault of transmission line are studied under the condition of weak current network. The results show that the transient overvoltage of PMSG is related to the capacity of wind turbines,the degree of voltage drop and the dynamic characteristics of phase locked loop（PLL）The simulation system model is built according to a real direct drive wind field to verify the conclusion.