The stability of μc-Si:H materials for solar cells was well researched. The light induced degradation of intrinsic μc-Si:H single layer material with different crystal volume fraction deposited were studied. The dependence of light-sensitivity as well as sub gap absorption on light soaking time was monitored. The results clearly showed that the magnitude of relative light induced degradation is closely related to material structure. Amorphous fraction is the key determining factor to light induced degradation. The results showed clearly that the magnitude of relative efficiency degradation is increase with amorphous fraction. The more amorphous fraction located in material, the more degradation was been found. With better structure and optical properties, microcrystalline silicon with transition region is more suitable for the manufacturing of stable Microcrystalline silicon solar cells due to the structure and optical properties.