Abstract: In this paper, the surface modification technology for Tianium alloy used in the fabrication of artificial joint is investigated. A layer of HAP, on which the muscle will grow easily, is coated on the Ti alloy substrate by Plasma spraying. In order to enhance the bonding strength between coating and the base metal, the TiO₂ added into the coating as additive. So, the influence of additive with different content on the bonding strength of the coating is investigated in detail. The bonding strength testing results show that adding additive TiO₂ can improve the bonding strength greatly, and with different content of additive will oblaine the different result. The fracture appearances are analyzed by means of SEM, which show that the toughness of the coating is improved by adding the TiO₂. Through XRD analysis of the coating, it is found that the TiO₂ in the coating can make some of the HAP decompose to produce new phase, such as α-TCP. It is these new phases that act as the toughenting role.