The invention discloses a 3D printing device of simulating an inner wall of a pipeline based on an additive manufacturing technology. The device comprises a main body mechanism, a traveling mechanism,a rotating mechanism and a 3D printing body, wherein the main body mechanism comprises a round rod, the travelling mechanism comprises three first rectangular rods and three second rectangular plates, wherein the left ends of the first rectangular rods are movably connected with the outer wall of the right end of a bearing through a hinge, driven wheels are rotationally installed at the right ends of the first rectangular rods, and through holes are formed in the middles of the first rectangular rods; and the right ends of the second rectangular plates are movably connected with the left endof the outer ring of an oil seal bearing through a hinge, the 3D printing body comprises a 3D printing gun head, and the 3D printing gun head is installed on a round pipe. The 3D printing device of simulating the inner wall of the pipeline based on the additive manufacturing technology can perform all-directional printing on the inner wall of the pipeline, printing is rapid, the printing effect isgood, 3D printing can be carried out on the inner walls of pipelines with different thicknesses, twining between a feeding pipe and a wire can be avoided, and the anti-corrosion effect is good.