In order to solve the problem of voltage sag, a method for preventing and controlling the voltage sag on the grid side is provided. Through the analysis of the correlation and conflict between the investment cost and economic loss in the prevention and control of voltage sag. An optimization model considering the voltage sag prevention scheme by reducing short-circuit faults on the grid side. Taking the IEEE 30 node system as an example, the genetic algorithm is used to simulate the model, and obtain the specific prevention scheme of the corresponding line.To achieve the purpose of reducing the investment cost of voltage sag prevention and control, and reducing the annual economic losses of voltage sags suffered by sensitive users of the entire network.