Mobile robots have broad application prospects in the fields of planetary exploration, outdoor detection, disaster search and rescue, and military. In order to design a small high-speed mobile robot that can replace humans in complex environments, this paper, focusing on sideways unstructured terrain, proposes a wheeled mobile platform with passive suspension. The structure is modeled, the mechanical calculation of the obstacle structure and the damping system was carried out，the dynamics simulation was proposed to evaluate the obstacle performance, and the power system and control system were selected and configured. A prototype was assembled and tested. The experimental results show that the prototype can adapt well to the sideways terrain.