The invention relates to an unsupported three-dimensional printing method of an oral diagnosis model. The method comprises the following steps: 1) directly scanning the oral cavity by an intraoral three-dimensional scanner to obtain dentition gingival STL data; 2) adding a pedestal plane approximatively parallel to a |occlusion| plane to a model in three-dimensional data editing software; 3) making the median sagittal plane of the digital model perpendicular to the plane of a printing platform, allowing anterior teeth upward; 4) making a horizontal spacing between two continuous layers of all surface data to be printed of the model in the Z-axial direction less than 1/2 of the thickness of a printing layer; 5) controlling a material nozzle to spirally print along a data surface; 6) setting the wall thickness of the model to be the optimum printing width of single feed; 7) setting the internal filling rate of the printing to be zero; and 8) generating a layered printing code, and inputting the layered printing code to three-dimensional printing control software of a printer in order to start printing. The method is suitable for the unsupported high-efficiency three-dimensional printing of three-dimensional scanning data of various models of the stomatology department.