Abstract: In order to assess open-pit mine transportation risk，a new assessment method based on the model of PSO-BP neural net was proposed.Taking the 15 transportation routes of an open-pit mine for example，seventeen major factors were selected as the second-level indexes of risk index system to make quantitative processing.The BP neural net model was built，and its weights and the threshold values were optimized with PSO algorithm.Depended on the risk scores of fuzzy comprehensive evaluation，a comparison of training results and test results between PSO-BP model and BP model was made respectively.Results show that the assessment results of PSO-BP model is greatly consistent with the actual situation and has higher assessment accuracy than that of BP model.The proposed PSO-BP evaluation model.

Key words: Transportation system, Risk assessment, PSO-BP model, Neural net, Particle swarm optimization