The invention discloses a three-dimensional model reconstructing method for keeping a fracture line of a jaw bone. The method is characterized by comprising the following steps that 1, CT data, in accordance with a Dicom protocol, of an injured jaw bone are input; 2, a surface model of the jaw bone is extracted by using a Marching Cube isosurface algorithm; 3, a segmentation algorithm which combines a Gaussian mixture model with Graph Cut is used for rapidly completing segmentation of broken bone blocks and a main bone block; 4, automatic replacement is conducted on the broken bone blocks on the basis of the symmetry, and a complete jaw bone model is obtained by splicing the broken bone blocks and the main bone block; 5, positioning devices which are each composed of a pair of coupling block devices are additionally arranged on the seams of the complete model obtained through splicing; 6, a complete three-dimensional solid model is obtained through assembling according to the positioning devices. By means of the three-dimensional model reconstructing method for keeping the fracture line of the jaw bone, in a jaw bone repairing operation, particularly when chimerism, fixation and repair are conducted between the broken bone blocks and between the broken bone blocks and the main bone block, the fracture line information of the defect parts is kept, so that errors in the operation are reduced, the wounds of a patient are reduced, the process of the operation is accelerated, and the operation effect is guaranteed.