Tantalum (Ta) as a new type of medical metal is now utilized in several orthopedic applications due to its excellent fracture toughness and workability,high corrosion resistance,good biocompatibility and X-ray visibility,but it lacks bioactivity.Therefore,pure Ta was hydrothermally calcified in CaHPO4 solution at 120-200 ℃ here for bioactive surface modification.Scanning electron microscopy (SEM),energy-dispersive X-ray spectroscopy (EDX),X-ray photoelectron spectroscopy (XPS),X-ray diffraction (XRD) and Raman spectroscopy analyses show that thin tantalum oxide film with a few calcium phosphate precipitates is formed at the surface after the treatment at 200 ℃.The hydrothermally treated sample has good hydrophilicity and corrosion resistance evidenced by the water contact angle measurement and the potentiodynamic polarization test,respectively,and it can induce the formation of apatite layer after soaked in the simulated body fluid for 1 week.The present method would be applicable for bioactive surface modification of tantalum implants with irregular shapes and even porous structure.