This study focuses on the reliability assessment of Press-pack IGBTs, crucial components in power electronics for ensuring stable system operation. Addressing the limitations of existing research, which often neglects the electrothermal coupling effects, we establish a comprehensive model that considers these effects. Through high-precision numerical calculations, we obtain key parameters such as electric field distribution, temperature distribution, and mechanical stress distribution. Experimental validation confirms the model’s accuracy in predicting Press-pack IGBTs’ performance changes and reliability under various operating conditions. This research not only enhances reliability assessment methodologies but also supports optimal design and practical applications of Press-pack IGBTs.