The development of injectable bone cement has been recognized as a promising strategy to fulfill the complex requirements of biomaterials for micro-invasive surgeries. The purpose of this study was to develop a novel injectable bioactive bone cement based on tricalcium silicate (TCS)-α-tricalcium phosphate (α-TCP) composites. Different bone cement formulations were prepared by varying the TCS contents (0, 3.2, 9.9 and 11.8% mole of TCS). The hydration experiments were carried out at 37o C. Injectabilities, setting times and mechanical properties of the final composites were determined. The results indicate that TCS delays the conversion of α -TCP into calcium-deficient hydroxyapatite (CDHAP). The produced CDHAP in the presence of TCS was modified by partial substitution silicate ion in place of phosphate. Also, Ca(OH)2 produced from TCS hydration inter CDHAP and increases the Ca/(P+Si) molar ratio.