The inhibition effect of hydroxyapatite (HAP) nanoparticles on hepatocarcinoma was investigated in vivo. The human hepatocarcinoma cell line Bel-7402 was transplanted subcutaneously into nude mice. Hydroxyapatite nanoparticles suspension at a dose of 0.2 mL was injected into the transplanted tumors every day for 2 weeks, and saline was used as control. The efficacy of hydroxyapatite nanoparticles on this carcinoma was surveyed and morphological changes of tissue and cells were observed by light microscopy and transmission electron microscopy (TEM). Experimental results show that hydroxyapatite nanoparticles have a visible destructive effect on the structures of hepatocarcinoma cells and tissue. The inhibition rates of tumor growth were 77.21% and 51. 32% after intra- tumor injection of hydroxyapatite nanoparticles for 1 week and 2 weeks, respectively. Compared with the control group, hydroxyapatite nanoparticles can also prolong the survival time of the nude mice bearing this cancer significantly. This indicates that hydroxyapatite nanoparticles have the therapeutic potential on hepatoma in vivo.