The problem of the mobility of the off-road vehicle over the roughness roads is studied. The vehicle model parameters is gain by the frequency offset tests. The road roughness is tested by testing the suspension displacement. The driver’s vertical acceleration sequence signal on the roughness roads is acquired. The absorbed power is calculated based on human tolerance limit. The ‘human-vehicle body-wheel’, three-degrees-of-freedom vibration model is built. And road roughness sequence signals by the inverse Fourier transform is worked out, which is the input of the simulation. Then the driver’s vertical acceleration sequence signal on the roughness roads is simulated utilizing the Simulink software. The speed at six-watts of absorbed power shows the mobility of the off-road vehicle passing through the roughness roads.