The adsorption and reactions of the SiHx (x = 0-4) on Titanium dioxide (TiO2) anatase (101) and rutile (110) surfaces have been studied by using periodic density functional theory in conjunction with the projected augmented wave approach. It is found that SiHx (x = 0-4) can form the monodentate, bidentate, or tridentate adsorbates, depending on the value of x. H coadsorption is found to reduce the stability of SiHx adsorption. Hydrogen migration on the TiO2 surfaces is also discussed for elucidation of the SiHx decomposition mechanism. Comparing adsorption energies, energy barriers, and potential energy profiles on the two TiO2 surfaces, the SiHx decomposition can occur more readily on the rutile (110) surface than on the anatase (101) surface. The results may be used for kinetic simulation of Si thin-film deposition and quantum dot preparation on titania by chemical vapor deposition (CVD), plasma enhanced CVD, or catalytically enhanced CVD.