In order to realize the lightweight design of large capacity fourway valve, combined with its structure characteristics and operation conditions, the finite element analysis model under ultimate pressure resistant working condition was established．Through the pressure blasting strength experiment, the correctness of the finite element model and strength analysis was verified．On this basis, the lightweight design of the fourway valve was carried out based on the theory of dimension optimization, and simulation analysis of compressive strength and experimental verification of the optimized model were carried out until meeting experimental specification for compressive strength of fourway valve．The results show that the strength of the lightweight designed fourway valve structure meets the specification requirements, and the stress distribution is uniform．The valve body quality is reduced by 14.07%,running up to reduce quality and save cost，and provide convenience for the onsite installation of airconditioning units，and improve the space layout of air conditioners．