A 3D printed and combined building wall element having a 3D printed external wallboard; a 3D printed internal wallboard; and a cement concrete layer sandwiched there between. A structural reinforcement component includes a plurality of vertical and horizontal steel reinforcements, the latter being continuously bent in a meander shape with a convex edge and a concave edge of each horizontal steel reinforcement being located in the 3D printed external wallboard and the 3D printed internal wallboard, respectively. The plurality of vertical steel reinforcements are located in the 3D printed external wallboard and the 3D printed internal wallboard and are fixed at inner folding angles of the plurality of horizontal steel reinforcements.