NOVELTY - Preparing polycrystalline silicon thin film comprises (1) cleaning a surface of the substrate by deionized water and then placing the glass sheet on the substrate and then introducing the substrate into a high purity acetone and high purity alcohol containing beaker and then carrying out ultrasonic cleaning for 10-20 minutes and washing the obtained product with deionized water and then drying, (2) opening a magnetron sputtering vacuum coating chamber for plating the sample in a sample rotating bracket, (3) opening a cooling water system and (4) carrying out vacuum-pumping process.    USE - The method is useful for preparing polycrystalline silicon thin film (claimed), which is useful in solar cell and integrated circuit manufacturing fields.    ADVANTAGE - The method prepares the polycrystalline silicon thin film in a simple, rapid and cost effective manner at low crystallization temperature and good quality.    DETAILED DESCRIPTION - Preparing polycrystalline silicon thin film comprises (1) cleaning a surface of the substrate by deionized water and then placing the glass sheet on the substrate and then introducing the substrate into a high purity acetone and high purity alcohol containing beaker and then carrying out ultrasonic cleaning for 10-20 minutes and washing the obtained product with deionized water and then drying, (2) opening a magnetron sputtering vacuum coating chamber for plating the sample in a sample rotating bracket, (3) opening a cooling water system, (4) carrying out vacuum-pumping process at pressure of 1-6x 10-4 Pa, (5) opening an argon gas bottle, a flow meter, introducing argon gas in a film plating chamber and then sputtering at air pressure of 1-6 Pa, (6) starting the radio frequency power supply target and then carrying out presputtering to remove silica and aluminum impurities on the target surface, (7) adjusting the silicon and aluminum target radio frequency power, respectively 10-30 W and 100-200 W, carrying out sputtering process under substrate rotation by a automatic control computer, (8) placing the silicon-aluminum composite film in a magnetron sputtering chamber, starting the temperature control power supply and then carrying out annealing at 500-600 degrees C for 30 minutes to 2 hours, (9) reducing the temperature of the sample to room temperature and (10) removing the thin film of aluminum deposited on the surface of the obtained product by etching solution containing phosphoric acid, nitric acid, acetic acid and water according to the ratio of 4:1:4:1.