Internal voids in insulators give rise to partial discharge, which causes a local breakdown and even entire insulation breakdown. Recently, the necessity of establishing the way to diagnose the aging of insulation materials and to predict of insulation breakdown become important. The purpose of our work are to investigate the treeing phenomena with an artificial needle shaped void by the charge of discharge and acoustic emission pulse in each phase angle area at the same time. We analyzed the .PHI.-QA-t pattern and .PHI.-AEA-t pattern using statistic operators such as pulse magnitude, pulse number, skewness, kurtosis. Therefore, the relation between the charge of discharge and acoustic emission pulse will be helpful to predict the breakdown just before the breakdown occur.