Hydraulic poppet valve often works in fluid-solid coupling state. It is necessary to comprehensively consider the multidisciplinary coupling effects in the design and optimization of poppet valves. This paper presents the fluid-solid coupling model for the optimization of a poppet valve, and the actual flow performance of the poppet valve is analyzed by numerical method. By coordinating the conflicting requirements at the system level, the MDO model of the poppet valve is built. The Multiple-island Genetic Algorithm is employed to solve the optimization problem, and an optimum design of the poppet valve is obtained. The optimization results show that the optimum poppet valve has a better performance on the flow characteristics.