Composite material poly(o-phenylenediamine)/manganese dioxide (PoPD/MnO2) used as supercapacitor electrode was one-step synthesized by liquid phase co-precipitation. To obtain good electrochemical performance, such as capacitance performance, rate capability and cycle stability, non-ionic surfactant P123 (poly( ethylene oxide)-poly(propylene oxide)-poly( ethyl oxide), PEO-PPO-PEO) is employed to regulate the morphology, structure and dispersity of PoPD/MnO2. As evidenced by infrared spectroscopy and X-ray diffraction, PoPD/MnO2 are all amorphous structure with weak crystallinity. It is worth noting that P123 imposes great influence on morphology, specific surface area and capacitance behavior of PoPD/MnO2. As P123 increases, PoPD/MnO2 initially presents as large irregular blocky aggregates, gradually evolves into near-spherical nanoparticles (50-80) nm, and eventually changes to the coexistence state of both. Sample PoPD/MnO2-0.8 obtained under the optimum P123 dosage 0.8 g (0.0035 mol L-1) has the largest Brunauer-Emmett-Teller specific surface area (123.2 m(2) g(-1)) and specific capacitance (292.4 F g(-1)) at 500 mA g(-1), much higher than that of PoPD/MnO2-O without P123 (47.2 m(2) g(-1) and 62.1 F g(-1)). Meanwhile, the rate capability and the cycle stability of PoPD/MnO2-0.8 improve significantly as well. The equivalent series resistance, electrons transfer resistance and diffusion impedance of samples prepared with suitable amount of P123 all reduced to some extent. (C) 2014 Elsevier Ltd. All rights reserved.