To solve the problem of compression deformation and gap bite during the assembly of O-ring seals and thin-walled cylindrical shells, a pressure fitting device is designed. This device is used for assembling sealing caps, sealing rings and shells. According to the assembly form of the parts, the mechanical structure design of the pneumatic device is completed and the electrical circuit is built at the same time. And cylinder selection and pressing force calculation are completed through numerical analysis software. A guide groove is designed according to the installing form of the sealing ring to achieve the closure of the rubber ring. Based on waveform springs, the elastic structure design is completed to achieve zero contact between the upper edge of the shell and the end face of the guide groove, and to avoide deformation and damage to the sealing ring during assembly. By calibrating the waveform spring objective function, the pre-installation force is set to improve the qualification rate and achieve device optimization.