The invention discloses a liquefaction device of hard bone, comprising: outer cavity having upper end detachably sealed with upper cover, and lower end openable/closable sealed with lower sealing cover, first liquefaction cavity coaxially slidably disposed in outer cavity, stainless steel cage disposed coaxially in first liquefaction cavity, second liquefaction cavity fixed to outer sidewall of outer cavity such that lower end portion of outer cavity is located in second liquefaction cavity. The invention also provides a method for co-production of bone collagen polypeptide and ultrafine bone powder based on liquefaction device, including: selecting hard bones, crushing； performing first-stage and second-stage liquefaction to obtain liquid phase and solid phase； centrifuging, concentrating, drying liquid phase to obtain bone collagen polypeptide； drying, coarsely and superfine pulverizing solid phase to obtain ultrafine bone powder. The invention has effects of simplifying process, improving production efficiency, and reducing production and equipment investments.
