Cobalt base alloys are widely used for dental and orthopedic implants due to their suitable mechanical properties, corrosion resistance and appropriate biocompatibility. These alloys are biologically inert and do not have the ability to make bonding with tissue. Implants coated with bioactive materials such as hydroxyapatite and bioglass show higher biological fixation in human body. Several coating techniques have been emerged, however, coating and surface bioactivation during the fabrication process is more desirable economically, while higher quality and saving time. Cobalt- Chromium – Molybdenum implants is generally fabricated by investment casting and usually followed by heat treatment. The purpose of this study was surface bioactivation of ASTM F-75 alloy through investment casting and solution treatment and investigation of coating properties. For surface bioactivation, molten metal poured in to molds which previously coated with hydroxyapatite via centrifugal casting. The mold preheating temperatures effect on coating properties were investigated. Several mold preheating temperatures were tested and temperature distributions obtained by numerical modeling. For surface bioactivation during solution treatment, the casting was heat treated in mixture of hydroxyapatite – bioglass media. Bioactivity was evaluated in vitro by specimens emersion in simulated body fluid. Specimens were characterized by X– ray diffraction analysis, electron scanning microscopy, energy dispersive spectroscopy and optical microscopy. Results showed the bioactive layer reached in calcium and phosphor on the surface of Cobalt – chromium – Molybdenum alloy substrates. In vitro evaluating bioactivity results and bone like apatite formation on surface which indicator as bioactivity showed the improvement in osteointigration of alloy when it used as a dental or orthopedic implant. Key words Investment Casting, Cobalt-Base Alloy, Bioactive Ceramics, Coating, Surface Bioactivation, Heat Treatment, Numerical Modeling