With the continuous improvement of the process level of integrated circuits, more and more chips are integrated into single package device, which promotes the development of electronic packaging towards system-level and large-size packaging. With the increasing size of the die wafer and packaging size, there are still many technical problems. Decreasing packaging thickness and mismatching thermal expansion coefficient between heterogeneous materials can lead to big warpage and other reliability problems. In order to improve the reliability of packaging structure and protect vulnerable interconnect joints, the underfill is usually used to fill the gap between interconnect joints and protect them, which improves the strength and reliability of packaging devices. In this study, the influence of underfill Tg point on adhesive strength and the effect of underfill performance parameters on packaging reliability (stress, deformation) are mainly analyzed through experiments combined with the finite element analysis method.