The frequent occurrence of large blackouts caused by distribution network failures has led to the study of the operational risks of the distribution network systems. Aiming at the increasing influence factors of operational risk in the development of the distribution network, a risk assessment model considering multiple influencing factors is proposed. In the model, the calculation of power outage cost of distribution network adopts a new method, which reflects the comprehensive impact of frequency, duration and cost, and can more scientifically calculate risk cost and make the risk assessment results of distribution network are closer to the fact. Finally, the Monte Carlo method was used to evaluate the risk of RBTS Bus-3, and compared with the evaluation results of the analytical method, so the validity of the evaluation method was verified.