The invention discloses controlled-release recombinant human bone morphogenic protein-2 poly-L-lactic acid microspheres and a preparation method thereof, which relate to a medicament carrier and preparation thereof. The component of a microsphere substrate is poly-L-lactic acid (PLLA); the wrapped medicament is recombinant human bone morphogenic protein-2 (rhBMP-2); and the released rhBMP-2 active protein is integral in structure and exists in a form of a homologous dipolymer. The preparation method comprises the following steps: mixing rhBMP-2 organic solution and PLLA organic solution to obtain mixed solution; precipitating microsphere crystals from the mixed solution after the mixed solution passes through a supercritical fluid CO2 solvent extraction; and after obtaining the microspheres, stopping pumping the mixed solution, keeping a pressure and a temperature in a high pressure autoclave unchanged, and continuously introducing CO2 to elute the microsphere crystals to remove residual organic solution. The method of the invention is simple in process, short in period, easy in organic solution removal, high in biological safety, short in burst releasing period and long in obtained microsphere particle controlled-release period, and easier in the storage of the physiological activity of the rhBMP-2.