We apply the first-principles calculations to study the structure, elastic modulus, Debye temperature and heat capacity of four TiH2. The results show that one new orthorhombic (Pnma) TiH2 is predicted. The tetragonal (I4mmm) TiH2 is more stable than the cubic (Fm-3m) TiH2. Compared to MgH2, TiH2 shows the strong deformation resistance. TiH2 dihydrides exhibit the strong bulk modulus compared to MgH2. The electronic structure shows that the high elastic modulus of TiH2 is determined by the Ti-H bonds. The Debye temperature of cubic (Fm-3m) and tetragonal (I4mmm) TiH2 is larger than the orthorhombic TiH2. The heat capacity follows the order of orthorhombic > cubic > tetragonal.