To study the impact of road roughness incentive condition on dynamic load of multi-axle heavy vehicle, this paper starts from the waveform state of the longitudinal section of the pavement surface. Dynamic differential equations of vehicle vibration model are established by using three-axis and four-axis heavy load vehicle models with balanced suspension structure. The effect of different pavement conditions and driving conditions on the dynamic load of the vehicle was analyzed using dynamic load indexes. The findings reveal that within a specific speed range, the inherent vibration frequency of the vehicle system approaches the excitation frequency caused by road roughness, resulting in the maximum dynamic load. The dynamic load factor is generally the largest at no load, the second largest at full load, and the smallest at overload. However, the combined effect of static and dynamic vehicle loads on the pavement structure should be considered. The heavier the vehicle, the lower the speed at which the vibration frequency and the incentive frequency of the road surface roughness are close to the resonance. For the two vehicle models, the most unfavorable pavement wavelengths for generating dynamic loads are 9 m and 12 m respectively. These research findings provide valuable insights for studying the response of pavement structures under dynamic loading conditions.