Hydroxypropyl-chitosan with substitution degree of 0.56 is prepared by the reaction of chitosan and epoxypropane by controlling condition. The water solubility of modified hydroxypropyl-chitosan is enhanced. When suitable concentration of hydroxypropyl-chitosan water solution responds to certain concentration of sodium polyphosphate based on ion gel method, the hydroxypropyl-chitosan nano-spheres with particle size of 500-700nm are obtained. Transmission electron micrograph shows that the shape of prepared hydroxypropyl-chitosan nano-sphere is uniform.