Double-channel experimental device used under microgravity for in-orbit fluid transport in space is designed. The device is used to observe the flow in open capillary channel under microgravity, and then the steady characteristic of flow transport is studied. The device with double-channel can observe the flow that has two kinds of sections and flow rate in single experiment. The double-channel device can improve the experimental efficiency and reduce uncertainty in contrast experiment. The key technology and difficulties of the design, such as sealing property and pressure compensation, are also discussed. The device system and experimental step are also presented. In microgravity conditions provided by drop tower, by using HFE7500 as fluid medium, the unsteady flow and steady flow are observed by the double-channel device.