This paper aims to improve the biocompatibility of Ti-15Mo alloy. Through micro arc oxidation (MAO) with Ca element replaced by Sr element in electrolyte and subsequent hydrothermal treatment, hydroxyapatite (HA) coatings are made on the surface of Ti-15Mo alloy. With the help of X-ray diffraction (XRD) and scanning electron microscope (SEM), this paper analyzes the microstructure, phase composition, contact angle and apatite inducing ability in the simulated body fluid of the coating. The results indicate that the MAO voltage under constant current mode is affected by the Sr concentration in the electrolyte and with the increase of Sr concentration, the scale and porosity of micro-pores of the coating with different Sr concentration first reduce and then increase. HA and Sr-HA phases had formed in the surface of Ti-15Mo alloy after MAO and hydrothermal treatment. Meanwhile, the Sr-HA crystallinity in the coating showed a rising trend with the increase of Sr concentration. The best Sr-HA crystallinity in coatings formed in the 30-Sr specimen, and the distribution of Sr-HA crystal columns with a stable hexagonal shape presented uniformly. In addition, the contact angle after hydrothermal treatment also presents excellent hydrophilicity, and the contact angle in 30-Sr specimen after hydrothermal treatment is 10.5°. Apatite induction ability of the coating of Ti-15Mo alloy in the simulated body fluid (SBF) has enhanced due to addition of Sr ions in the electrolyte during the MAO. The best apatite induction ability and biocompatibility of the coating appear in 30-Sr specimen, and its apatite deposition thickness is 58.87 μm. Apatite induction ability of Ti-15Mo alloy can be significantly improved by adding strontium ions in the electrolyte. When 30% Sr ions are added into the electrolyte, the apatite induction ability of the coating is the best and it also has good biocompatibility.