Biodegradable polymer microparticles bearing a steroid drug and a preparation method therefor. In the method, a steroid drug and a biodegradable polyester-based polymer are dissolved in an organic solvent and sprayed into a low-temperature hydrocarbon solution to form frozen microparticles that are then immersed in a low-temperature, aqueous salt solution to deprive the microparticles of the organic solvent, thereby preparing biodegradable polymer microparticles bearing a steroid drug. The steroid drug or steroid sex hormone drug-bearing biodegradable polymer microparticles were found to have excellent biocompatibility, biodegradability, porosity, and mechanical strength and to release the steroid drug or steroid sex hormone drug for a long period of time.