3D Printed and Combined Building Wallboard (100, 200, 300) including external decorative plate (7), 3D printed external wallboard (1), cement concrete layer (9), 3D printed internal wallboard (2), internal decorative plate (8), and structural reinforcement component (10). Structural reinforcement (10) includes vertical steel reinforcements (5) and horizontal steel reinforcements (11) continuously bent in a convex-concave way along the lengthwise direction. The convex edge and the concave edge of each horizontal reinforcement (11) are respectively located in the wallboard of 3D printed external wallboard (1) and the wallboard of 3D printed internal wallboard (2). External decorative plate (7) is fixed on 3D printed external wallboard (1), internal decorative plate (8) is fixed on 3D printed internal wallboard (2), and the space between 3D printed external wallboard (1) and 3D printed internal wallboard (2) is filled with cement concrete layer (9). Thermal insulation (15) is provided between external wallboard (1) and concrete layer (9), and may be between internal plate (8) and internal wallboard (2).