To analyze the dynamic characteristics of U-type road under moving vehicles, the coupled vibration problem is decomposed into two independent motion system, i.e. vehicle vibration subsystem and road vibration subsystem. The displacement coordination equation of wheel and pavement is used to consider the contact of vehicle and road. Based on the formula derivation of vehicle vibration differential equation, the dynamic responses of U-type road is analyzed and studied with the 3-D spatial distribution of road surface roughness considered. The results show that the fluctuation of vehicle-road coupling force is small when the road surface is smooth. The vehicle-road coupling force increases rapidly with the deterioration of road conditions. The forces of left wheel and right wheel is different under the non-uniform excitation of road surface roughness. Vehicle speed has little effect on the dynamic load coefficient comparing with road surface roughness. The impact of vehicle load should be considered under poor road conditions.