In order to analyze the influences of the factors of the towing attachment on the longitudinal riding comfortability of a tractor trailer combination, an eightdegreeoffreedom model of the tractor trailer combination was constructed. The simulation programme of the tractor trailer combination riding comfortability has been designed; the infulences of the stiffness and the damping coefficient of the towing attachment, the speed of the combination,the road surface roughness and the load of the combination on the riding comfortabillty of the tractor trailer combination were analyzed by means of the theoretical simulation and experiments.