NOVELTY - Preparing low-crystalline nano-hydroxyapatite by membrane modulation and mineralization method, by dissolving type I collagen in hydrochloric acid inside dialysis bag, adding calcium chloride and type I collagen outside dialysis bag, pouring calcium chloride solution to concentrated phosphoric acid, adding prepared sodium hydroxide solution to calcium chloride-phosphoric acid solution, adding obtained solution to inorganic calcium salt solution, maintaining dialysis bags in inorganic calcium salt solution, taking out bags and filtering white solution.    USE - Preparation of low-crystalline nano-hydroxyapatite used in artificial bone and as drug carrier or medical biomaterial for preventing and treating osteoporosis and healing bones by inducing osteogenesis when implantation on a receptor and injected with medical fluorine.    ADVANTAGE - The method enables preparation of nano-hydroxyapatite having low crystallinity even at high calcination temperature. The nano-hydroxyapatite is degradable. The method enables controlling bioactive components of the biomimetic hydroxyapatite in an easy manner. The nano-hydroxyapatite is stable, uniform and biocompatible.    DETAILED DESCRIPTION - Preparing low-crystalline nano-hydroxyapatite by membrane modulation and mineralization method, involves (a) dissolving commercially available type I collagen in 0.01-0.5 mol/l hydrochloric acid inside a dialysis bag, and stirring solution uniformly to obtain collagen solution having concentration of 0.1-15 weight/weight%, (b) preparing inorganic calcium salt solution outside the dialysis bag by (i) adding commercially available calcium chloride and type I collagen in a mass ratio of 1-10:10-1 to obtain calcium chloride solution having concentration of 0.01-5 mol/l, (ii) pouring 85% calcium chloride solution (based on calcium ions) to concentrated phosphoric acid in a molar mass ratio of 1.67:1, and (iii) adding commercially available sodium hydroxide and calcium chloride in a mass ratio of 10-1:1-10, adding obtained sodium hydroxide solution to the solution containing calcium chloride and phosphoric acid, stirring and mixing solution, and further adding the solution to the inorganic calcium salt solution, and (c) adding the collagen solution in dialysis bag having predetermined molecular weight cut-off to the inorganic calcium salt solution, stirring at 1-40 degrees C for 0.5-24 hours, taking out the dialysis bag, obtaining white colored solution and filtering the white colored solution using 0.45 mu m filter to obtain low-crystalline nano-hydroxyapatite.