Addressing the challenge of uni-directional fluid flow without power input in a semi-circular tubular microchannel, a large-scale model inspired by the Nepenthes alata peristome was designed and fabricated, with a scale of 100 μm. The mechanism behind the uni-directional liquid spreading was examined, leading to the design of a semi-circular tube structure featuring the Nepenthes alata peristome surface. A digital light processing 3D printer using a photocuring method was employed to create the workpiece. Experimental studies were conducted to observe the uni-directional spreading of liquid within this large-scale semi-circular tubular microchannel. By calculating the range, various structural parameters' influence on the liquid's uni-directional spreading performance was quantified. Results indicate that the semi-circular tubular microchannel, characterized by factors such as the ellipse's semi-major axis of 570 μm, microcavity wedge of 30°, microchannel width of 320 μm, structural length of 360 μm, stretching length of 200 μm, and curvature of 2, showed superior uni-directional spreading performance. The influence of each factor on the spreading coefficient, ranked from smallest to largest, was stretching length, structure length, microcavity wedge, semi-major axis of the ellipse, microchannel width, and curvature. These findings offer essential guidance for the design parameters of large-size semi-circular tubular microchannels with a Nepenthes alata peristome structure and also confirm the feasibility of using conventional 3D printing technology to create microchannels with uni-directional fluid spreading.