Generally, the vibration analysis of vehicles takes road roughness as displacement excitation, ignoring the effect of the geometric relationship between wheel and road. This paper analyzes the influence of the crawler-vehicle bogie wheel’s diameter on the displacement excitation and deduces the equations for the calculation of the displacement excitation, considering the influence of the track filtering effect and wheel’s diameter. Then, the vertical vibration state equations and corresponding simulation model were formulated, and the vibration of a vehicle moving on the wavy and practical road were analyzed. The results showed that the analysis that considered the crawler-vehicle bogie wheel’ s diameter better simulated the practical conditions with more information. Finally, experiments verified the ability of the proposed method to calculate displacement excitation.