The degradation behaviors of hydrogenated amorphous/microcrystalline silicon (a-Si:H/µc-Si:H) tandem solar cells are systematically investigated. It is found that the degradation of the tandem solar cells takes place not only under the light soaking but also after dark storage. The degradation in the efficiency of tandem solar cells is mainly due to a reduction of fill factor (FF) in our study. Different from light-induced degradation (LID) behaviors for the tandem solar cells, the degradation behaviors under dark storage, i.e., the dark degradation could be mainly caused by the cracks or voids formed in the bottom µc-Si:H cell. These defects could lead to an oxidization of internal silicon surfaces by the oxygen atoms. The stabilities of the top a-Si:H cells and the ZnO:B electrodes are also investigated. Furthermore, adjusting the crystallinity of intrinsic µc-Si:H material and inserting an intermediate light reflective (ILR) layer between the top cell and bottom cell can improve the performances of the novel structure tandem solar cells. A gain of 0.7% in efficiency is achieved, and meanwhile no dark degradation is observed for the novel tandem solar cells.