Textile-based electrode materials have attracted intensive attention for flexible supercapacitors. However, the low electrochemical capacitance hinders their further application. In this study, MnO2 with high theoretical capacitance was successfully deposited on the conductive graphene/polyester composite fabric using a hydrothermal method. The MnO2 morphology can be controlled by adjusting the reaction time. The effects of MnO2 morphology, electrode structure, mechanical bending and stretching on the electrochemical performance of MnO2/graphene/polyester composite electrode materials were studied in detail. When a MnO2 sheet layer deposited on the graphene/polyester composite fabric, the resulted composite electrode material exhibited a specific capacitance of 332Fg−1 at a scan rate of 2mVs−1 and excellent cycling stability. The electrochemical performances of MnO2/graphene/polyester composite electrode material and its corresponding solid-state supercapacitor device were stable under mechanical bending and stretching conditions.