Although great progress has been achieved in numerical simulation on porous flow in rock in decades, experiments performed on reservoir-on-a-chip (ROC) have been emphasized as the most sufficient and direct way to investigate the subsurface fluid flow at pore scale. This paper applies the cutting-edge three-dimensional printing (3DP) technique into the fabrication of ROC and the visualized two-phase fluids experiments. The structure of 3D-printed ROC is quantitatively characterized using the surface scanning analyzer and stereomicroscope, and then validated by comparison with the original digital structure. Then immiscible (oil-water) two-phase flow experiments are conducted on the 3D-printed ROC and imaged using the high-resolution camera in real time. The typical fingering phenomenon caused by the heterogeneity of pore-throat structure is observed, and the effects of surface wettability on the interfacial shape evolution are analyzed. Comparing to traditional fabrication methods (e.g., chemical etching and soft lithography), 3D-printed ROC is approved to be a novel approach to manufacture the morphology, topology, and connectivity of the pore network, while reducing the cost and the time required.