The invention relates to a preparation method of a degradable and release-controllable polymer carrier, in particular to a preparation method of a release-controllable electrospun fiber drug carrier with a nested nanostructure. The method comprises the following four steps: preparing carrier particles, preparing electrostatic spinning fluid, preparing a spinning fiber membrane and carrying out aftertreatment on the fiber membrane; the obtained fiber membrane can be both applied to the exterior of a body and implanted into the body, and has good biological activity, biodegradability, antibacterial property and good drug loading property; furthermore, lignin nanoparticles wrapped in spinning fibers show a certain antibacterial property in a degradation process of the fiber membrane; in addition, the fiber membrane prepared by the method can be biodegraded in a long-term service period in the alkaline environment of body fluid, so that the stable release of a drug is ensured, and the drugis enabled to be fully and thoroughly released.