An assembly structure of an optical film and a frame is provided. The optical film has a body and at least a positioning structure protruding from the edge of the optical film. The positioning structure has a sticking part and a neck. The neck is connected between the sticking part and the body. In addition, the frame is arranged to surround the optical film, and the frame has at least a slot. The positioning structure is located within the slot, and a restriction protrusion corresponding to the neck of the positioning structure is formed on the frame at an entrance of the slot, so that the sticking part of the positioning structure is restricted within the slot.