This study sought to compare the biocompatibility of four dental ceramics so as to provide indications useful for the further development of dental materials. Osteoblasts were obtained by culturing the cranial explant of SD rat and cultured in vitro when they were seeded onto four different materials: hydroxyapatite, bioactive glass ceramics, tricalciumphosphate-hydroxyapatite and nano-hydroxyapatite (nHA). The phase contrast microscope and scanning electron microscope were used to evaluate the cell morphology and attachment. The content of alkaline phosphatase was calculated by molecular biological methods. MTT method was performed to find the alteration of proliferation. Then by use of wash way method, the adhesion ability was tested. The results showed that all of the four bioceramics had good cytocompatibility. There were significant differences among them on the levels of cell growth, differation and adhesion in vitro. The biocompatibility of nHA is the best and of conventional HA is the worst.