This paper presents the heat transport performance of a Flexible Looped Heat Pipe (FLHP) with the working fluid of ammonium under microgravity condition. The evaporator of the FLHP has two coaxial wicks. The outer wick is made of PTFE with 1.2μm pore diameter and the inner one is made of Polyethylene with 12μm pore diameter. The inside surface of the inner wick is axially grooved. the core of the inner wick is used as liquid reservoir so that reliability of the operation can be enhanced. As the results of the experiment, the FLHP performed normally under microgravity condition and had the predicted capillary limit. the FLHP showed good temperature control ability and was like a VCHP in the range of 150∼240W heat transfer rate. Liquid behavior observed in the visual module assured the normal operation of the second wick and inner axial grooves under microgravity condition.