Abstract: Car tracing trail is a bad taffic safety accident in expressway,and more and more people pay attention to it. In recent years people try to solve carelude tracing trail both in theories and technologies. This paper shows that withsome characteristics, ultrasonic imaging technology is clearly superior to optimalimaging technology and radar imaging technology in car elude tracing trail. On thebasis of combining with signal processing, modal recognition, computer imageprocessing, computing aptitude, data-base, expert system, sensor, singleship,communication, ultrasonic imaging technology have good emploitation value andapplication foreground for car elude tracing trail in expressway.