Abstract: To mimic the components and structure of the natural bone, chitosan (CS) and hydroxyapatite (HA) were selected as the macromolecule and the source of the calcium phosphate, respectively. The raw materials were dissolved in an acid solvent to form homogeneous solution, and then underwent sol-gel phase transition and aging procedure to prepare nano-HA/CS porous composite scaffolds in situ. The effects of aging time and pH value on the composition, micromorphology and compressive strength of the HA/CS composites were studied. The results show that the compressive strength and modulus of the scaffolds decrease obviously with the increase of the pH value, and the compressive strength is higher than pure CS scaffolds when the pH is 10 and 11. XRD results indicate that the transition of phosphorus calcium to HA can be impelled with the aging treatment, and the growth of HA crystallites orients along the c- axis in the crystal structure. SEM results reveal that the scaffolds possess inter-connected porous structure, and the rod-like or grainy nano-hydroxyapatite crystal particles disperse uniformly in the scaffolds, which formed homogeneous dense organic/inorganic composites. This kind of fast and deep mineralization method for preparation of bone scaffold provides a new way of thinking.