Cauliflower MnO_2was prepared by hydrothermal synthesis method by reacting MnSO_4and (NH₄)₂S₂O_8with Fe(NO₃)₃. The samples were analyzed by X-ray diffraction(XRD) and scanning electron microscopy (SEM ). Cyclic voltammetry and galvanostatic charge-discharge were used to characterize the electrochemical performance of the samples. The results show that the prepared samples are α-MnO₂.The particles are in a cauliflower shape. In an electrolyte of 6mol/L KOH , electrode based on the MnO_2show perfect supercapacitor characterization in the potential region of 0~0.4V. At a current density of 100mA/g , a specific capacitance of 176F/g is achieved.