Abstract: Investigates the cruise control for an off-road vehicle with automated mechanical transmission. The cruise control system (CCS) functions are analyzed and the program flow chart of the CCS developed. A fuzzy PID control strategy is developed for the CCS. Relations between the K<sub<<</sub</em<P<em<,K<sub<<</sub</em<I<em<,K<sub<<</sub</em<D and speed error E and error change rate E<sub<<</sub<em<c are established. Based on a large number of tests and the experiences of skilled drivers, fuzzy control rules are developed. Experiments of entry and exit of the cruise control system and engine responses at different speed errors are conducted on a test bench. Also, comparison experiments between the fuzzy PID and PID are accomplished. Experiment results showed that the developed cruise control system has a good performance.