MnO2 is considered as one of the most promising electrode materials for flexible supercapacitors but it often suffer in poor conductivity, which limits practical applications according to industry needs. To enhance the performance, forming MnO2-based hybrid structures with conductive materials is a promising implement approach. Ti3C2Tx MXene sheets, a new kind of 2D transition metal carbides with metallic conductivity and hydrophilic nature, are promising candidate to couple with MnO2. According to the complementary principle, we design a novel structure MnO2/Ti3C2Tx hybrid nanocomposite by synergistically coupling one-dimensional (1D) MnO2 nanoneedles with two-dimensional (2D) Ti3C2Tx MXene sheet for flexible supercapacitor. XPS investigations suggest the obvious charge transfer from Ti3C2Tx sheets to MnO2 nanoneedles, where Ti3C2Tx sheets serve as a remarkable 2D conductive substrate to facilitate the electrons transfer in the nanocomposites. This strong synergistic effect between Ti3C2Tx and MnO2 resulting from the chemical interaction greatly enhance the electrical conductivity, specific capacitance, rate stability and structural stability of the MnO2/Ti3C2Tx nanocomposite. To show the potential application in energy storage, a symmetrical flexible supercapacitor device with good electrochemical performance, high flexibility and super cycling ability is fabricated by utilizing MnO2/Ti3C2Tx nanocomposites as electrode materials. This work has proposed a new approach of developing advanced nanocomposites from a MnO2-based electrode for high performance flexible electronics.