Among the natural factors which can cause accidents to power grid, the typhoon disaster is one of the most serious. In order to enhance the ability of power grid to withstand typhoon disaster, a typhoon disaster early warning method for power grid is proposed, which can realize short-term early warning of typhoon disaster for power grid quantitatively. Firstly, the warning area is divided into 0.01°×0.01° grids by longitude and latitude and the set of grids ω which have transmission lines inside is sorted out. Then according to the typhoon information provided by the meteorological administration, the effective decision boundary is obtained through comparing the distance from the center of grid in set ω to the center of typhoon with the wind radius of level ten. Thus the risk set of lines is determined using effective decision boundary, and the early warning level of typhoon disaster can be obtained by calculating the outage probability of risky lines. Meanwhile, the corresponding warning information should be released, providing basis and reference for the operating staff of power grid to work out the targeted control plan for grid stability and scheduling strategies of preventing typhoon disaster.