Abstract: Vacuum feedthrough, which is one of key components of the ion cyclotron range of frequencies (ICRF) antenna, is applied to seal for the ICRF antenna. In view of the importance and safety of the vacuum feedthrough, the finite element methods (FEM) were utilized to perform the thermal and thermal mechanical analysis for two types of the vacuum feedthroughs. The distributions of temperature and stress for two types of the vacuum feedthroughs were demonstrated. The results show that the temperature and the stress in the vacuum feedthrough coated with silver are lower than those in the vacuum feedthrough coated without silver. However, the stresses in the vacuum feedthroughs coated with and without silver are all below the allowable stress, which demonstrates the feasibility and safety of two types of the vacuum feedthroughs.