A 3D printing head, comprising: a feeding pipe, provided with an opening at its bottom structure; a shutter, disposed at the opening and slidably connected to the bottom structure, wherein the opening comprises a region occluded by the shutter and a region not occluded by the shutter, and the region not occluded by the shutter forms a discharge port of the 3D printing head, wherein the discharge port comprises a first end and a second end, and the distance between the first end and the second end define a length of the discharge port; and a drive apparatus, connected to the shutter, wherein the drive apparatus receives a control instruction of a control apparatus and drives the shutter sliding at the opening according to the control instruction of the control apparatus to adjust a position of the first end and/or a position of the second end at the opening, so as to adjust the length of the discharge port; wherein in a process of filling a target filling region in a current layer, the drive apparatus drives the shutter sliding at the opening according to the control instruction of the control apparatus to adjust the position of the first end and/or the position of the second end at the opening, so that projection positions of the first end and the second end in a vertical direction are located on the cross-sectional contour line of the target filling region, and the length of the discharge port matches lengths of intercept line segments of a cross-sectional contour line of the target filling region along a length direction of the discharge port, wherein the target filling region is part or all of a filling region of the current layer; characterized in that the bottom structure of the feeding pipe is provided with a plurality of discharge ports, and the plurality of discharge ports are configured such that when an intercept line of a cross-sectional contour line of the current layer along an opening direction is intercepted into multiple line segments, the different discharge ports correspond to different target filling regions in the current layer and the 3D printing head print the current layer completely through one unidirectional straight line movement; wherein in the process of filling the target filling region, the 3D printing head moves along a one-way straight line under a control of the control apparatus. a feeding pipe, provided with an opening at its bottom structure; a shutter, disposed at the opening and slidably connected to the bottom structure, wherein the opening comprises a region occluded by the shutter and a region not occluded by the shutter, and the region not occluded by the shutter forms a discharge port of the 3D printing head, wherein the discharge port comprises a first end and a second end, and the distance between the first end and the second end define a length of the discharge port; and a drive apparatus, connected to the shutter, wherein the drive apparatus receives a control instruction of a control apparatus and drives the shutter sliding at the opening according to the control instruction of the control apparatus to adjust a position of the first end and/or a position of the second end at the opening, so as to adjust the length of the discharge port; wherein in a process of filling a target filling region in a current layer, the drive apparatus drives the shutter sliding at the opening according to the control instruction of the control apparatus to adjust the position of the first end and/or the position of the second end at the opening, so that projection positions of the first end and the second end in a vertical direction are located on the cross-sectional contour line of the target filling region, and the length of the discharge port matches lengths of intercept line segments of a cross-sectional contour line of the target filling region along a length direction of the discharge port, wherein the target filling region is part or all of a filling region of the current layer; characterized in that the bottom structure of the feeding pipe is provided with a plurality of discharge ports, and the plurality of discharge ports are configured such that when an intercept line of a cross-sectional contour line of the current layer along an opening direction is intercepted into multiple line segments, the different discharge ports correspond to different target filling regions in the current layer and the 3D printing head print the current layer completely through one unidirectional straight line movement; wherein in the process of filling the target filling region, the 3D printing head moves along a one-way straight line under a control of the control apparatus.