BACKGROUND: Studies regarding synthesizing composite bone repair materials with organic macromolecules as mineralizers template are the hot research spot. However, reports concerning using agar as bone repair materials are few. OBJECTIVE: To synthesize a novel agar-hydroxyapatite composite material, and to evaluate its physical and chemical properties as well as cytocompatibility.METHODS: ①A certain amount of the non-nano-hydroxyapatite in hydrochloric acid solution was added into a certain amount of agar sol, and the reaction system was adjusted with PH value of 7-8. And then the precipitate was lyophilized to obtain the composite of agar-hydroxyapatite.②The third generation of rat bone marrow stromal cell (BMSC) was co-cultured with agar-hydroxyapatite. And the growth of cells was observed at days 1, 3 and 5 after culture. RESULTS AND CONCLUSION: The results of X-ray diffraction patterns, Fourier transform infrared spectrometer (FTIR), thermal analyzer, transmission electron microscope, and scanning electron microscope showed that agar could manipulate the growth of hydroxyapatite, and hydroxyapatite nanocrystals was equably formed on the agar-fibers with high porosity. The BMSC grew well in the composite and form a clear cytoskeletal at days 3 and 5 after culture. The results reveal that agar-hydroxyapatite composite has good physical and chemical properties and cytocompatibility.