Nano-HAP (10-20nm) were obtained from East China University of Science and Technology. The osteoblasts were primary cultured from rat calvaria and then treated with five different concentrations(20，40，60，80，100µg/ml) of nano-HAP, the osteoblasts without nano-HAP was used as control group. Inhibition ratio, apoptotic rate were evaluated by MTT assay and flow cytometry (FCM), respectively. The specific surface area of nano-HAP was detected by BET. All date were expressed as mean ± standard deviation.Statistical analysis was performed by t test using software SPSS11.0 for Windows. The results indicated that the nano-HAP could inhibit the growth of osteoblasts in a dose-dependent manner. When the concentrations of nano-HAP were 20, 40, 60, 80, 100µg/ml, the inhibition ratio were 2.8%, 22.2%, 26.9%, 38% and 47.7%, and the apoptotic rate were 4.63%, 6.75%, 9.47%, 11.49%, 17.22%, respectively, which were obviously higher than that of control group. The nano-HAP significantly induced apoptosis in osteoblasts. There were the same tendency that the apoptotic and inhibition ratio of osteoblasts were rising with the increasing of the concentration of the nano-HAP. The specific surface area of nano-HAP was 148.140m2/g.