Abstract: Since the modern society has an increasing dependency on the electricity, the power blackout will cause massive losses and impacts on the grid. How to evaluate comprehensive loss caused by blackout is the problem both government and grid enterprises pay special attention to. A social comprehensive evaluation indicator system and corresponding evaluation model for the impact caused by blackout are established based on public security model, and the quantitative evaluation is performed in the aspects of social personnel casualties, property loss and loss due to delay in service restoration. Theoretical analysis on the parameter of the established model and the optimization of the assigned values for the model parameters are carried out. According to the statistics data of blackout in a city, the social comprehensive loss after blackout is calculated and compared with calculation results of typical blackout events occurred around the world, and the rationality of the proposed evaluation model is verified.