Along with the development of online monitoring intelligent system on power transformer, the reliable research conclusions on type identification, strength calculation and accurate positioning were urgently needed for the measurement of partial discharge. In this paper, all the partial discharge were classified into 5 patterns based on the principle of partial discharge in transformer. Two group of testing model were built using air and transformer oil separately as the insulating materials respectively. The characteristics of different partial discharge were studied by specified test circuit in high voltage laboratory, through the comparison of data from spectrum analyzer, oscilloscope and 3-D spectrogram. The test results show that the discharge along surface has the most destructive and every kinds of discharge has different characteristics, which can be used for pattern identification and provide references for the discharge accurate position.