In this paper, the authors designed ultrasonic ranging system for marking vehicle. This system consists of an ultrasonic module, DSP, temperature compensating module, LCD and keyboard. LM1812 was adopted to transmit and receive ultrasonic wave information. The digital signal processor TMS320LF2407 was used to control the ultrasonic system, select and process data. The distance between road-lineation vehicle and the reference objective was calculated based on reflecting time of ultrasonic wave and thus the accuracy position of the vehicle was determined. The simulation test showed that the measuring range of ultrasonic ranging system was 60~700cm. The measuring errors of the ultrasonic ranging system were less in the range of 100~500cm.