Abstract: Objective　Preparation of modified bone morphogenetic protein-2 polylactic acid sustained-release nanosphere (rhBMP-2-mPEG-PLA-Ns) for the purpose of bone formation, and to study their physical and chemical properties and release studies in vitro. Methods　rhBMP-2-mPEG-PLA-Ns was prepared by emulsion The surface morphology of the nanosphere was observed by perspective electron microscope, laser particle size distribution of the nanospheres was tested by Malvern laser. Encapsulation efficiency and drug loading of the microspheres were measured by ELISA. Release delivery rate in vitro was tested by the dynamic dialysis drug Determination. Result　The nanospheres have smooth, rounded surfaces and uniform particle size. The particle size of the nanospheres was ranged between 45 ~ 50nm. Encapsulation efficiency and drug loading were respectively (78.2±1.81)% and [(2.24±0.24)×10-5]%. The release in vitro found no burst release, the release rate was 23.47% in 24 hours，and was 78.56% within 21 days. Conclusions: rhBMP-2-mPEG-PLA nanospheres had a good physical and chemical properties and sustained release effect, and had a good foundation for further applications.