Considering serious damage to sensitive load caused by the voltage sag, this paper proposes an improved emergency voltage control method. It installs STATCOM device and sheds load coordinately to compensate voltage to improve the voltage sag probability index. Firstly, based on the Monte Carlo method, fault model is built to calculate voltage sag occurrence probability. Then, the total annual cost function is put forward, which solves the minimum cost to get optimal capacity of the STATCOM. Further, according to different failures causing different failure severity to a node, an emergency load control is introduced. Combining the STATCOM with shedding load, the STATCOM is used to compensate voltage as the first priority. When the STATCOM compensation reaches its limit, it will shed the load to prevent and reduce the voltage sag occurrence probability as far as possible. Finally, an example of Dongguan district in Guangdong province is simulated, the results show that the method mentioned is correct and effective.