The present invention relates to inorganic bone graft materials and a method for preparing the bone graft materials. Particularly, the present invention relates to a method for preparing bone graft materials comprises the following steps: collecting cancellous bones from an animal; removing lipids and organic materials from the cancellous bones using organic solvent, sodium hypochlorite and hydrogen peroxide; and sterilizing the cancellous bones wherefrom the lipids and the organic materials are removed. The bone graft materials prepared by the method of the present invention meet requirements for use in bone grafting, including biocompatibility, sterilization, osteoinductivity and osteoconductivity with free from immunogenecity and toxicity to tissue and are suitable for use in osteogenesis and have morphogenesis.