Abstract: Double-sided cooling insulated gate bipolar transistor (IGBT) modules have gradually become the first choice for electric vehicle power devices due to their advantages such as low thermal resistance, high power density, and small parasitic inductance, while their packaging reliability has also attracted widespread attention. Although many manufacturers and scholars have conducted power cycling research on various materials inside the modules, it remains unclear whether the epoxy resin that is in direct contact with the chip and the three-layer solder affects the power cycling lifetime of double-sided cooling IGBT modules. In this paper, power cycling tests under identical conditions are performed for both transfer-molded double-sided cooling IGBT modules with epoxy resin and those without epoxy resin. The test results demonstrate that epoxy resin can enhance the solder lifetime of double-sided cooling IGBT modules, thereby improving power cycling lifetime, but it may also lead to chip failure. The influence mechanism of epoxy resin on double-sided cooling IGBT modules is explained through ultrasonic scanning before and after testing as well as power cycling simulation. The research results can provide guidance for semiconductor device manufacturers in designing and manufacturing double-sided cooling IGBT modules.