The health status of transmission lines directly affects the stability of the system, so how to accurately assess the risks in line operation is very important. Based on the proportional hazard model, the paper constructs a risk probability model of overhead lines by comprehensively considering the climate and the health probability of individual equipment; builds a big data platform, and uses the numerical fitting method to solve the parameters of the above probability model; finally, uses the above model to carry out risk assessment on transmission lines. The simulation results show that the construction of the big data platform has improved the computing speed, and the obtained model parameters are more accurate; the use of the comprehensive probability model can accurately evaluate the status of the transmission line, which has guiding significance for the operation and maintenance personnel to maintain the equipment.