Abstract: Under the condition of stationary random stimulation, the dynamics differential equations of the tractor-trailer combinations have been set up, and in order to improve their riding comforts, the deterministic parameter system has been solved. The flexible drawing of the tractor-trailer combinations has been optimized, the simulation analysis of the dynamics equations and the riding comfort tests have been performed. The results showed that the use of the flexible drawing could improve the drawing status and the riding comfort conditions of the tractor-trailer combinations greatly under the condition of stationary random stimulation.