The existing studies usually ignore the influence of external force damage caused by small animals and trees on real-time failure rate, and it is difficult to accurately calculate the undetermined coefficient in the real-time failure rate index model based on health index. Therefore, a method is proposed to calculate the real-time outage probability of distribution network based on the combination of fault factor parameter correction and health index model. Firstly, the historical failure rate of distribution equipment for many years is calculated according to the month, and then, the historical failure rate is modified through using the method based on the parameter correction of fault factors. Meanwhile, the synergistic effect between the main fault factors is also taken into account to some extent. The correction value of the failure rate is substituted into the real-time failure rate model based on health index to determine the undetermined coefficient in the exponential model. Then, the feeder partition method is adopted to calculate the failure probability and outage time of each load point. Finally, the effectiveness of the proposed method is verified by the route in Guangzhou area.