With the continuous economic development and the continuous increase of vehicles, the number of traffic accidents has become more frequent. In order to alleviate the road traffic safety problem, this article takes a traffic accident in an urban area of Shandong Province on National Highway 205 as an example. Based on the traditional fault tree model, this paper proposes Two sensitivity and importance algorithms are used. The two algorithms rely on inverse trigonometric functions, inverse proportional functions, and partial derivative calculations. Through related calculations, it is found that the important factors affecting traffic accidents in an urban area of Shandong Province on National Highway 205 are: poor visibility, lighting conditions Poor, other facters, no central isolation fence, old and weak, non-motorized vehicles illegally on the motorway.