Si film anode was prepared by ion beam assisted deposition for Li ion batteries. The crystal structure, morphology and electrochemical performance of Si film were investigated in detail. The results show that the Si film is amorphous. The intercalation/deintercalation voltages of the Si film were at 0.03V and 0.16 V as well as 0.34 V and 0.49 V. The Si film exhibits high specific capacity and efficiency, which are 3134.4 mAh/g and 87.1％ in the first cycle, respectively. Furthermore, the Si film shows superior cycle performance. The capacity retention is 92.2% after 200 cycles at 0.5C rate.