In this work, a hydrothermal method has been exploited to synthesize porous delta-MnO2 nanosheets. The influence of hydrothermal temperature on the synthesis of delta-MnO2 has been investigated by using X-ray diffraction (XRD), scanning electron microscopy (SEM), N-2 adsorption-desorption isotherms, transmission electron microscopy (TEM) and electrochemical methods. The results show that the pure delta-MnO2 appears at the hydrothermal temperature from 130 to 170 degrees C, and the hydrothermal temperature has a great influence on the morphology and BET surface area of as-prepared samples. The delta-MnO2 prepared at 150 degrees C delivers high specific capacitances of 411 F g(-1) at a scan rate of 5 mV s(-1) and 332.7 F g(-1) at a current density of 0.5 A g(-1). The excellent supercapacitor performance is attributed to the porous nanosheets structure, which brings a large specific surface area, increases the active sites, and shortens the ion diffusion distance in delta-MnO2 electrodes. It is suggested that the optimal synthesizing temperature is 150 degrees C in order to obtain pure delta-MnO2 with good electrochemical performance by hydrothermal method.