Aiming at the complexity of terrain in the hilly area of Southern China and the lack of traffic ability of traditional farmland transportation vehicles, an eightwheel unmanned ground vehicle with bionic hydraulic swing arm mechanism was proposed and designed. The vehicle was driven by hydraulic motor, controlled by line of sight remote and steers by slipping. The posture of the vehicle can be adjusted by four swing arms to adjust to accommodate different forms of ground barriers. The obstaclesurmount performance was the fundamental factor that restricted the adoption of the platform. So the unmanned vehicle attitude planning model and the obstaclesurmount dynamics model were established, and the barrier performance of the unmanned platform in the typical vertical obstacle was obtained. In order to verify the theoretical analysis, a secondary development simulation platform was established in ADAMS, and a prototype experiment on dynamics was carried out. The research result showed that the eightwheel fourarm unmanned ground vehicle can climb vertical wall with height of 1.13 times the diameter of the tire by the posture planning and dynamics performance, and had a good ability to pass through the complex ground environment to meet the walking demand of agricultural transport vehicles in the hilly terrain in complex farmland terrain.