Supermultiple-point-electrode conductance probe method has recently become realistic for examining the interfacial structure in gas-liquid two-phase Bow. A new instrument based on this method was developed and applied into vertical downward gas-liquid two-phase flow. The graphics of interfacial profiles are presented on typical flow patterns briefly and on plug and foam Bows in detail. It is pointed out that the plug flow lies in the two regions separated by the foam Bow, which was newly found in this study. The interfacial profiles of gas slugs depend strongly on the slip velocity of gas slug to the liquid phase in liquid slug, and the two regions of plug flow are classified into the low and high slip velocity groups. In the former group slip velocity is mostly negative. Furthermore, some findings are introduced on the prediction of the void fraction in liquid slug, on its relation with the two flow regions of plug Bow, and on a characteristic property observed in the fluctuation of pressure gradients for foam flow.