The freeze plug is an important passive safety system used in the molten salt reactors (MSRs). However, although the inclination angle is one of the fundamental design parameters, its influence on the freeze plug performance has not been explored systematically. Multidimensional numerical simulations were hence carried out to analyze the effects of tube inclination on the solidification and melting processes of salt encountered in the freeze plugs of the MSRs in this work. The effects of placing a high thermal conductivity cover plate on the outer wall of the freeze plug were also investigated. In the solidification process, the tube inclination had a significant impact on the equilibrium shape of the frozen salt. A decrease in the inclination angle from the horizontal resulted in a reduction in the plug volume, and closing of the freeze plug became more difficult when the inclination angle was small and the tube diameter was large. In the melting process, natural convection induced in the liquid salt was intensified with a decrease in the inclination angle. This accelerated the melting of solid salt to shorten the opening time significantly. Optimizing the tube inclination angle was hence shown to be of great importance to improve the safety of MSRs. When a copper plate was placed on the freeze plug outer wall to facilitate the heat transfer to the frozen salt, its influence on the solidification process was not noticeable, while melting was accelerated and the opening time was reduced by about 20%.