Abstract: The present invention relates to a preparation method of drug-containing sustained release microparticles, the preparation method comprising the steps of: (a) dissolving a biodegradable polymer and a drug in a halogenated alkane solvent to form a drug-containing biodegradable polymer solution; (b) homogeneously mixing the drug-containing biodegradable polymer solution in a continuous phase containing a surfactant to form a dispersed phase; (c) maintaining an emulsion comprising the continuous phase and the dispersed phase at a temperature lower than the boiling point of the halogenated alkane solvent to form microparticles in the continuous phase; (d) primarily drying the microparticles; (e) mixing the primarily dried microparticles with an aqueous alcohol solution, and then maintaining the aqueous alcohol solution at a temperature no less than the boiling point of the halogenated alkane solvent to extract and evaporate the remaining halogenated alkane solvent from the microparticles; and (f) secondarily dryi