The invention relates to a method for preparing an environment-friendly hydrophilic porous coating used for modifying the surface of a porous membrane, and belongs to the technical field of porous membrane coating production. The method includes the following steps: soaking the porous membrane subjected to oxidation by a potassium permanganate/hydrochloric acid solution into a hydroxy ethyl cellulose (HEC) emulsion containing or without containing aluminium oxide particles for 10-14 hours; taking out and placing into a refrigerator for 10-14 hours; then freeze-drying for 2-4 hours to obtain the hydrophilic porous coating. The preparation technology of the coating is simple and environment-friendly; the hydrophilic coating provided by the invention not only has a porous structure but also enables the porous membrane to have excellent wettability; in addition, the heat-shrink resistance of the holes is greatly improved; the coating has a wide application prospect in membrane separation of hydrophilic mediums and the battery industry.