tricalcium phosphate(α TCP)/tetracalcium phosphate(TTCP) composite bone cement had good hydration characteristic.In our system,α TCP/TTCP powder mixture was mixed with water at a powder/liquid (P/L) ratio of 1.50g·mL -1 .The setting time could be adjusted,the maximum compressive strength was 45.36MPa,and the hydration product was hydroxyapatite (HAP).In vitro biological simulated experiments indicate that α TCP/TTCP bone cement has α certain dissolubility.The hardened product is mainly HAP after soaking in simulated body fluid (SBF) for 10 weeks.The results of in vitro test and animal experiments and SEM analyses show that no local or general toxicity response,no muscle stimulation,no haemolysis,no cruor,no inflammatory reaction and no exclusion response are caused by α TCP/TTCP cement, which can be contributed to bone tissue spreading and impinging.α TCP/TTCP cement hydrated and hardened continually in vivo.The materials fused with host bone together with implanting time prolonging.Therefore,it is believed that α TCP/TTCP composite bone cement has a high biocompatibility and bioactivity,a certain biodegradation and good osteogenesis as well. tricalcium phosphate (α TCP) / tetracalcium phosphate (TTCP) composite bone cement had a good hydration characteristic. In our system, α TCP / TTCP powder mixture was mixed with water at a powder / liquid (P / L) ratio of 1.50 g · mL -1 The setting time could be adjusted, the maximum compressive strength was 45.36 MPa, and the hydration product was hydroxyapatite (HAP). In vitro biological mode Homogenization experiments indicate that α TCP / TTCP bone cement has α certain dissolubility. The hardened product is mainly HAP after soaking in simulated body fluid (SBF) for 10 weeks.The results of in vitro test and animal experiments and SEM analyzes show that no local or general toxicity response, no muscle stimulation, no haemolysis, no cruor, no inflammatory reaction and no exclusion response are caused by α TCP / TTCP cement, which can be contributed to bone tissue spreading and impinging. α TCP / TTCP cement hydrated and hardened continually in vivo. The materials fused with host bone together with implanting ti me prolonging.Therefore, it is believed that α TCP / TTCP composite bone cement has a high biocompatibility and bioactivity, a certain biodegradation and good osteogenesis as well.