Abstract: The traffic black-spot cause of formation is very complex, and every black-spot has the most important inducement for itself. The identification and improvement of black-spot, as an important task of traffic safety management, are very effect measures to reduce the traffic accident frequency. For the complexity and diversity of the black-spot cause of formation, we find a method based on the rough set to determine the most important inducement of the black-spot, then we can repair the inducement in effect and save more time and money.