Utilizing the dual functions of activated carbon (AC) both as a conductive agent and an active substance of a positive electrode, a hybrid supercapacitor (AC-MnO2&AC) with a composite of manganese dioxide (MnO2) and activated carbon as the positive electrode (MnO2&AC) and AC as the negative electrode is fabricated, which integrates approximate symmetric and asymmetric behaviors in the distinct parts of 2V operating windows. MnO2 in the positive electrode and AC in the negative electrode together form a pure asymmetric structure, which extends the operating voltage to 2V due to the compensatory effect of opposite over-potentials. In the range of 0–1.1V, both AC in the positive and negative electrode assemble as a symmetric structure via a parallel connection which offers more capacitance and less internal resistance. The optimal mass proportions of electrodes are calculated though a mathematical process. In a stable operating window of 2V, the capacitance of AC-MnO2&AC can reach 33.2Fg−1. After 2500 cycles, maximum energy density is 18.2Whkg−1 with a 4% loss compared to the initial cycle. The power density is 10.1kWkg−1 with an 8% loss.