In general, it is believed that the charge storage ability of MnO₂ as electrode materials of supercapacibility sorts as α-MnO₂>d-MnO₂>γ-MnO₂ in series. In this study, the polymorphy of MnO₂ were synthesized directly at room temperature by the ball milling of KMnO₄, MnSO₄.H₂O and NaOH using different synthetic media with different doping leve of Ca₂₊. Deionized water as the medium results in α-MnO₂, while absolute ethanol results in γ-MnO₂. Very slight dopant of Ca₂₊, such as lower than 100ppm, leads to lattice distortion and partial transformation to γ-MnO₂ from α-MnO₂. The hybrid phase is benefit to the increase of charge storage ability of MnO₂. The polymorphy of MnO₂ can be modulated by some impurities, such as Ca₂₊. The charge storage ability of MnO₂ as electrode materials of supercapacibility can be determined as, hybrid phase(a and g) of MnO₂>α-MnO₂>γ-MnO₂ by cyclic voltammetry analysis.