This thesis dealt with a LabVIEW-based algorithm which is capable of analyzing and recognizing partial discharge(PD) pattern for insulation diagnosis of Gas Insulated Switchgear(GIS). Protrusion on the enclosure surface and the conductor, void inside epoxy, and floating particle were fabricated to simulate the insulation defects in GIS. A high frequency current transformer(HFCT) with frequency bandwidth of 20kHz ∼ 30MHz is used to detect PD pulse. Also, a low noise amplifier with frequency bandwidthof 500Hz∼45MHz at a gain of 40dB was fabricated. The data acquisition module consists of a 2-channel analog input with a sampling rate of 100MS/s, 8bit vertical resolution, and bandwidth of 50MHz high cut-off frequency. A phase resolved partial discharge analysis(PRPDA) algorithm with a LabVIEW was fabricated. Features of each defect were analyzed by calculating the mean, the variance, the skewness and the kurtosis depending on the phase of applied voltage, while the algorithm adopts a defect when it appears within the deviation of ±10% of its statistic figure. From the result, it was verified that the proposed algorithm can detect PD pulse and recognize the types of defects in GIS on real-time basis.