The rapidly growing industry today makes the safety requirements of electric power requirements increased. Because the small size and high safety of SF6 gas insulated switchgears, they have been widely used in many industrial applications. To prevent the unexpected accidents of insulation deterioration, the correct detections and analyses are necessary. In this work, the acoustic signals, transferred out with a waveguide and an acoustic sensor, were recorded for analysis. These acquired signals were analyzed with the ensemble empirical mode decomposition (EEMD). This method is used to extract the implied empirical mode functions of input signal and to overcome the mode-mixing problem of empirical mode decomposition (EMD) method. According to the results of this work, it is found that the EEMD method does eliminate the mode missing effects, and provide the clearer spectrum distribution than that of EMD method. For the partial discharge analysis, EEMD method is a useful tool that can extract the implied information.