To improve the working performance of the compound rings high-pressure vessel, the different assembly and structural parameters during the process of radial and axial preloading have been analyzed with the finite element method. The simulation analysis on the assembly process of room temperature press-fitting has been carried out based on the theory of contact problem with friction, and it is found that the tangential compressive prestress is uneven under the influence of friction coefficient and conicity of fitting surfaces. The main effect factors of horizontal fracture of cemented carbide core are also analyzed. Furthermore, the results of reducing the axial stress of core by different ways of applying end pressure are compared. These studies provide the guidance for the improvement in design and manufacture of compound rings.