The invention discloses a preparation method of a porous microsphere. The method mainly comprises the following step of performing electric injection by electric injection liquid containing polymers for drug carriers, a first solvent and a second solvent under the electrostatic spinning condition. The invention also provides the porous microsphere prepared by the method, and a drug carrying microsphere using the porous microsphere as a carrier. The invention also provides a preparation method of the drug carrying microsphere and the drug carrying microsphere prepared by the preparation method. The invention also provides application of the drug carrying microsphere to the preparation of medicine for treating mucosa-associated diseases. The obtained drug carrying microsphere has strong mucosa adhesion force and high slow-release effects.