Abstract: In order to build steady high magnetic field experimental devices of water-cooled magnets, a structural design was made for a water-cooled magnet vessel. In the design plan, the capping was composed of three circular steel plates which were welded in the superimposed form, and the cylinder consisted of two layers: the inside cylinder and the outside cylinder, each including the upper and lower parts. The structural model of the vessel, designed by the three-dimensional drawing software Solidworks, was transferred to COSMOSWorks for the finite element analysis of stress and displacement. According to the design standards of pressure vessels, various kinds of stresses of the vessel were assessed by the stress intensity estimation criteria. The results show that the maximal displacement of the vessel was 0.499 mm, and the strength, displacement and security of the vessel met the design requirements.