To prepare natural nano-HA and a natural nano-hydroxypatite/chitosan (CH) composite and to study the biocompatibility of natural nano-hydroxypatite/chitosan composite. Natural hydroxyapatite (HA) was prepared from animal’s bone according to a calcining method, the natural nano-HA was prepared by using planetary ball milling, and the composite was prepared via in-situ precipitation. TEM and SEM were used to observe the size of natural nao-hydroxypatite and the microstructure of the composite. The biocompatibility of natural nano-HA/CH composite was evaluated by MTT test. The TEM micrography of the natural nano-HA showed that the size of the particles is below 100nm, and the composite reported in this study has layer-by-layer structure. The result of MTT-test showed the cytotoxicity level of the prepared composite was 0. The nano-HA/CH composite has good biocompatibility, and it can be potentially applied as internal fixation of bone fracture.