Abstract: A cloud model evaluation method was proposed according to the characteristics of fuzziness and randomness in road traffic safety evaluation. The evaluation indexes and standards were determined by analyzing the factors effected road traffic safety. The cloud model of each factor on each level was generated by each factor's cloud digital characters. The road traffic safety levels were determined by the weighted average value of the maximum membership. Data measured in the second ring road of Xi'an were evaluated. The results showed that road traffic safety was relatively safe in East Second Ring,South Second Ring and North Second Ring,and the membership of U( Ⅱ) were 0. 404 8,0. 609 8 and 0. 497 6respectively. Road traffic safety was basically safe in West Second Ring,and the membership of U( Ⅲ)was 0. 621 2. The results were compared with Grey evaluation method and Fuzzy Mathematics method.Not only the evaluation method based on the cloud model can determine road traffic safety,but also can determine the membership more accurately.