The utility model relates to medical plaster, particularly a plaster back adhesive film. The utility model is characterized in that the film of the utility model is a boan film (Boanflim) which is made of PU (polyurethan-polyurethane) materials. The film has favorable skin closing performance, ventilation properties and elastic properties. The film is cemented on the skin of a human body; the film can firmly fix a plaster body 1 to the corresponding part of skin, and can not freely desquamate so that drug effects can be ensured to be got into the body. Additionally, patients who are cemented with the back plaster are not required of worrying about plaster desquamation and wound infection in hydrophilic activities.