The invention discloses a method for customizing an expander according with biomechanics through laser scanning, finite element analysis and the 3D printing techniques. The method for customizing the expander according with biomechanics through the laser scanning, finite element analysis and 3D printing techniques comprises the following three steps that (1) according to body surface three-dimensional data obtained through the laser body surface scanning technique, an expander bottom surface which is attached to a to-be-expanded area is designed; (2) the stress conditions of all portions of skin at the end of expanding are known through finite element analysis software, the shape of an expanding bag is adjusted according to the stress conditions, curvature adjustment is conducted on the part, under overpressure, of the skin, and the expanding bag which can apply pressure to the skin dispersedly is designed; and (3) a water guide pipe and an injection valve are additionally arranged based on the expanding bag, and the expander is customized through the 3D printing techniques. According to the method for customizing the expander according with biomechanics through the laser scanning, finite element analysis and 3D printing techniques, the stress conditions of the skin at the end of expanding are known through the finite element analysis software, and curvature adjustment is conducted on the part, under overpressure, of the skin, so that the expanding bag which accords with biomechanics is designed, the risk of skin ulceration in the expanding process is lowered easily, and the expanding efficiency is improved.