Intelligent transportation system (ITS) is a complicated system, and selecting the shortest path is the core of the system. In order to ease traffic congestion of the city, through solving the shortest path, the key technology in realizing the function of ITS, and based on the analysis of traditional Dijkstra algorithm, the paper puts forward the improved algorithm. The new algorithm includes two parts, that is, preprocessing and real-time pruning research, and the effect of pruning totally depends on the division of specific diagram.