A large size self-sustained film with considerable thickness ranging from 30 μm to 500 μm was prepared through sol-gel method by adopting dimethyldiethoxysilane/tetraethoxysilane composite material as precursors. The film exhibits satisfactory plasticity and film forming capability as well. AFM (Atomic Force Microscope) investigation of the film surface showes a mean roughness of 0.3 nm. Gas chromatogram/mass spectrum analysis indicates that a large amount of ［(CH3)2Si-O］n molecules were formed during the hydrolysis and condensation processes. These molecules act as space filler within the gel network. Such filler not only leads to the structural flexibility and plasticity of the film, but also inducess the substantial decrease of the capillary forces and shrinkage in the film.