A method for detecting an alignment film coated on a substrate of a liquid crystal panel comprises: obtaining an image of an alignment film test region of a substrate; and analyzing continuity of the alignment film along an internal boundary of the alignment film test region in the image obtained. since the alignment film test region is located outside an active display area of the substrate, when the alignment film along the internal boundary of the alignment film test region is determined as continuous, it can be determined that all the edges of the alignment film are outside the active display area, then a Haro region which might appear on the edge of the alignment film may also be located outside the active display area, so as to ensure uniform thickness of the alignment film in the active display area of the substrate.