A slicing method for three-dimensional colored object, the slicing method comprising: a) importing a 3D file through a processor, the 3D file storing a 3D object; b) the processor performing a 3D route slicing for the 3D object to generate a plurality of printing routes corresponding to a plurality of printing layers; c) the processor performing a 2D image slicing for the 3D object to generate a plurality of image files corresponding to the plurality of printing layers, where each of the printing layers is corresponding to one or more image files including at least one of a cyan image file, a magenta image file, a yellow image file, and a black image file; d) the processor storing the printing route of one of the printing layers in a route file, wherein the route file is a G-code file; and e) after the step d), the processor storing a jetting command for one or more image files of the one of the printing layers in the route file, and storing a jetting route of the one of the printing layers in the route file, wherein each jetting command comprises at least one of a label C representing the cyan image file, a label M representing the magenta image file, a label Y representing the yellow image file, and a label K representing the black image file, and each jetting route comprises a jetting origin and a jetting destination for one or more image files corresponding to each of the printing layers; wherein the jetting command and the jetting route in the route file are used in a coloring operation of a printing device to control a 2D print head of the printing device to jet ink and to move to the ink-jetting destination marked in the jetting route based on one or more image files. a) importing a 3D file through a processor, the 3D file storing a 3D object; b) the processor performing a 3D route slicing for the 3D object to generate a plurality of printing routes corresponding to a plurality of printing layers; c) the processor performing a 2D image slicing for the 3D object to generate a plurality of image files corresponding to the plurality of printing layers, where each of the printing layers is corresponding to one or more image files including at least one of a cyan image file, a magenta image file, a yellow image file, and a black image file; d) the processor storing the printing route of one of the printing layers in a route file, wherein the route file is a G-code file; and e) after the step d), the processor storing a jetting command for one or more image files of the one of the printing layers in the route file, and storing a jetting route of the one of the printing layers in the route file, wherein each jetting command comprises at least one of a label C representing the cyan image file, a label M representing the magenta image file, a label Y representing the yellow image file, and a label K representing the black image file, and each jetting route comprises a jetting origin and a jetting destination for one or more image files corresponding to each of the printing layers; wherein the jetting command and the jetting route in the route file are used in a coloring operation of a printing device to control a 2D print head of the printing device to jet ink and to move to the ink-jetting destination marked in the jetting route based on one or more image files.