A flexible asymmetric supercapacitor (ASCs) is successfully developed by using the composite of MoO3 and graphene oxide (GO) electrochemically deposited on carbon cloth (CC) (MoO3/rGO/CC) as the negative electrode, the MnO2 deposited on CC (MnO2/CC) as the positive electrode and Na2SO4/polyvinyl alcohol (PVA) as gel electrolyte. The results show that the introduction of GO layer can remarkably increase the specific capacitance of MoO3 from 282.7 F g-1 to 341.0 F g-1. Furthermore, the combination of such good electrode materials and a neutral gel electrolyte renders the fabrication of high-performance ASC with a large operating potential difference of 1.6 V in 0.5 mol L-1 Na2SO4 solution of water. Furthermore, the ASCs exhibit excellent cycle ability and the capacitance can maintain 87 % of its initial value after 6000 cycles. The fact that a light-emitting diode can be lighted up by the ASCs indicates the device’s potential applications as energy storage devices. The encouraging results demonstrate a promising application of the composite of MoO3 and GO in energy storage devices.