The crystal structure models of α-titanium and β-titanium with hydrogen were established and the stable structure was optimized. The variation of volume, volume expansion rate, lattice constant and ratio of lattice constant for the α-titanium and β-titanium with hydrogen were calculated with help of the first principle method. The calculated results show that the hydrogen content affects the angle of crystal axe and volume expansion. Hydrogen would occupy the tetrahedral space of β-titanium at the hydrogen content below 0.2597wt% and/or the octahedral space of β-titanium at the hydrogen content above 0.2597 wt%