In order to effectively surrogate the traditional evaluation method based on the accident data,the calculation method of carfollowing safety distance including the membership function of weather condition in the microscopic fuzzy inference system for risk perception was improved.The whole road risk perception index was put forward to measure the total driving environment and the average risk evaluation indicator of rearend collision was developed for macroscopic traffic flow.The value of the average risk indicator could be achieved by simulation of AIMSUN software.Then,the Fuzzy cmeans cluster method was used to develop the criterion of the indicator.Therefore,the research results can provide a support for the early warning technology of traffic accidents.