The effects of alkali treatment on the deposition of apatite on various titanium alloy substrates have been studied. The results show that a porous titanium dioxide hydrogel layer with negative charge forms on the substrate during alkali treatment, and the gel layer can induce apatite formation in the simulated body fluid(SBF). The pore diameter, gel thickness and the induction ability of the gel layer increase with the concentration, temperature and treating time of the alkaline solution. The induction abilities of the various substrate materials decreases according to Ti>TC4, Ti75>TiZr. It is concluded the titanium alloys treated by alkali can induce apatite formation in SBF, and are bioactive.