A fuzzy controller for backing up control of truck-trailer system is proposed based on the single input rule modules dynamically connected fuzzy inference model. The relative angle of the truck with the trailer, trailer angle, and trailer vertical position are selected as the input items. The dynamic importance degrees are set up such that the relative angle takes control priority when it becomes big. Simulation results demonstrate that the fuzzy controller backs up the truck-trailer system successfully even from a jackknife situation.