In accordance to the drawback of amphibious vehicle's low speed in water, a new kind of folding mechanism based on double wishbone suspension is proposed. Referring to the working conditions of the wheel lifted mechanism, the hydraulic circuit, which provides with the functions of pressure limiting, locked and pressure retaining, is designed to ensure the accuracy of wheel lifted and the driving safety. The appropriate hydraulic cylinders, hydraulic components and auxiliary components are chosen due to the hydraulic system load and the maximum flow rate.