The method, characterized in that, the powdered chitosan is dissolved in water to obtain a 5% solution, into which a 70-90% acetic acid is added and after the formation of the blank intramedullary nail and carrying a coagulating bath and neutralization bath it is subjected to a crosslinking bath in a solution formed from 0.5 to 2% of sodium tri-polyphosphate and 0.5% to 3% Na3PO4 for 24 to 48 hours in temperature of 50° C. to 140° C. and then it is subjected to the drying process, for a period of 6 to 10 days, and finally the surface of the blank is treated to form the intramedullary nail. The surface treatment is carried out until the surface of the intramedullary nail contains at least 20%-40% of the pore of the depth of 0.1 mm to 1 mm.