The invention discloses a cross color and mixing printing method of a color 3D printer. The method comprises the steps that a rotating body is rotated, and extrusion heads communicated with runners are adjusted; due to the fact that the rotating body is arranged on the lower bottom face of a supporting body and can rotate around the axis of the rotating body, the lower bottom face of the rotatingbody is provided with a plurality of extrusion heads arranged in an evenly spaced manner in the circumferential direction, connectors in one-to-one correspondence communication with the extrusion heads are formed in the contact end face of the rotating body and the supporting body, wherein the number of the connectors is the same with that of the extrusion heads, and one connector is communicatedwith one of the runners; each extrusion head can only extrude same raw materials of the single color, through rotation of the rotating body, cross color printing can be achieved; a color mixing runnercommunicated with a single-color runner is formed in the supporting body, the feeding end of the color mixing runner is connected with a mixing mechanism, when the extrusion heads in the vertical state are communicated with the color mixing runner through the single-color runner, mixing materials can be extruded.