mu c-Si:H thin films have been deposited on the 7059 glass substrate by RF-PECVD. Effects of film thickness on structure and properties of Si thin films were investigated by XRD, Raman, UV-Vis and precision multimeter. Experimental results indicated that uniform dense microcrystalline silicon thin films can be prepared by rf-PECVD, silicon thin films transferred from a-Si:H to mu c-Si:H along with film thickness increased. For mu c-Si:H, XRD spectrum occurred (111), (220)and (331) peak, grain size and crystalline volume fraction increased with thickness enhanced, arrived at 82%; optical band gap of mu c-Si:H is 2.0 similar to 2.36eV and decreased when thickness increased, the transmittance was added firstly and then reduced with film thickness increased, the transmittance curve occurred redshift; the photosensitivity of the thin films was improved firstly and then decreased with thickness increased, which was highest at 104 quantity in the transition zone from a-Si:H to mu c-Si:H.