The present invention relates to a method for preparing polymer microparticles by a spray process, wherein a polymer solution obtained by dissolving a polyester-based polymer in ethylene carbonate (hereinafter, referred to as “EC”), which is a solvent, is sprayed at a low temperature hydrocarbon or alcohol solution, thereby preparing frozen EC/polymer microparticles, the frozen EC/polymer microparticles are dissolved in a salt aqueous solution, thereby dissolving and removing EC, and the residual EC in water is removed by washing.