In a packed bed system, the interfacial tensions of liquid drops highly affect their flow behavior by changing the direction of the interfacial tensions in the liquid-solid-gas interface. The vertical directional interfacial forces of a liquid drop in a packed bed of small particles were calculated using a 3-D analytic calculation model. Regardless of the wettability of a solid surface, the interfacial tension induces the resisting force against the gravitational force. In short, the interfacial tension limits the flow of a liquid drop along the direction of the gravitational force. In case two liquid drops of different phases directly contact each other in a packed bed, one of the interfaces of each drop is shared, and the influence of the interfacial force decreased so that the liquid drops could move down through the void between particles compared with the case a single drop. If the shared interface of two liquid drops of which one is non-wettable and the other is wettable has lower contact angle than that of the liquid-gas interface of the liquid drop, then the drops experience the downward force along the direction of the gravity in the larger range of the position in the packed bed.