Abstract: The structure stability and diffusion behavior of interstitial hydrogen in stoichiometric TiC bulk are investigated by first-principles calculations. The results indicate that interstitial hydrogen in stoichiometric TiC bulk prefers to be trapped by the C atom(C-HS) with C—H bond length of 1.15 Å(1 Å=0.1 nm), and its formation energy is 1.58 eV after ZPE correction, followed by the center position of Ti/C cube(CS) with formation energy of 1.75 eV after ZPE correction. The hydrogen in CS configuration is mainly hybridized with neighboring Ti atoms. The optimal diffusion path of interstitial hydrogen in TiC bulk is consisted by the “jumping” diffusion in Ti/C cube with energy barrier of 0.47 eV, then followed by twice “rotating” diffusion through Ti/C plane with energy barrier of 0.28 eV.