Abstract: The mechanism of crack of the 3D-stacking modules after temperature cycling test were studied, and the modules were encapsulated by epoxy resin. The analysis proves that, the defect in the process of encapsulating is the main factor which leads to the crack, therefore during curing process of the resin, the contraction stress and the thermal stress playing an important role in the development of the defect. Finally the specific solutions were proposed from several aspects, such as optimizing the curing process conditions of the resin, improving the CTE matching performance between different materials, and advancing the resin casting process. All these measures above can enhance the reliability of the 3D-stacking modules.