A digital image measurement device for measuring a specimen surface deformation based on sub-pixel corner recognition, the device comprising: an image-measurement pressure chamber, a CMOS industrial camera, a camera support (15), a flexible lens hood (14), and a computer and matching measurement software. Further provided is a digital image measurement method for measuring a specimen surface deformation based on sub-pixel corner recognition. The method comprises discretizing a specimen (4) into several four-node finite elements by means of squares printed on the specimen (4), wherein the corners of a grid act as the nodes of each finite element; tracking deformation of a feature point in real time based on sub-pixel edge detection and corner recognition; capturing full-surface deformation information of the specimen (4) by means of a plane mirror (3) with an angle of 120 degrees between the two faces thereof behind the specimen (4); and performing splicing and error correction on three images to achieve full-
