In this study, three kinds of underfill materials were used to investigate the enhancement of silane coupling agents on the adhesive strength of the underfill and the silicon substrate undergoing boiling water soaking. Adhesion properties between the underfill and the silicon were evaluated by shearing test. The fracture interfaces of the shearing tests are observed by SEM. The results show that the adhesive strength between the silicon and the underfill decreases significantly without silanes, and the bonding between the resin and the filler becomes loose by hydrothermal aging. Underfill containing aminosilane has higher water resistance, which can improve the adhesive strength of underfill, and can help to strengthen the bonding between underfill and filler after hydrothermal aging.