In this work, the laser diposition process of Si thin film at low temperature and under low pressure is studied. We obtain both poly-crystalline and non-crystalline films, the sizes of them are about a few cm2, and they are satisfactorily homogeneous. The optimum condition of diposition process is determined care-fully. When the pedestal temperature is 380°, poly-crystalline films are formed. Based on the model of photo-breakdown of SiH4 through resonant absorption of laser and energetic Si-atom formation induced by the shock waves produced thereafter, the laser plasma CDV dynamic process is analysed. We find that the photo-breakdown of SiH4 by TEA CO2 laser and the induced shock waves have important influuences on the growth of Si films. The sizes and crystalline structure of Si films as calculated theore tically agree qualitatively with experimental results.