Abstract: With the development of insulated gate bipolar transistors (IGBTs) towards high voltage and high power, the heat and operating temperature they generate are escalating rapidly, thereby making the failure of their insulating package systems increasingly prominent. In order to meet the increasingly harsh working environment of IGBT, there is an urgent need to develop a high-performance silicone packaging material. In this paper, phenyl modified silicone gel (PMSG) is prepared by chemical synthesis, and heat resistance and dielectric properties of PMSG are studied emphatically. The results show that, the thermal weight loss temperature of PMSG at 5% weight loss is 383℃, and the breakdown field strength at room temperature can reach 32.62 kV/mm, which is 17.42% higher than that of pure silicone gel (PSG). And the breakdown field strength at 150℃ is only 25.38% lower than that at room temperature, which exhibits better electrical resistance at high temperatures. Meanwhile, it has lower dielectric loss compared to PSG. Therefore, when PMSG is used as an IGBT packaging material, the overall performance is better. This research will provide effective ideas and theoretical basis for the development of novel high-performance insulation materials for IGBT packaging.