Abstract: To eliminate the bombardment of feedback ion to a photocarhode of a Gen. Ⅲ LLL night vision system and increase its operating lifetime，the preparation technique of depositing a Al2O3 ion-feedback barrier film on MCP was investigated by low-magnetron sputtering technique. The optimal depositon conditions for preparing the ion-feedback barrier film on MCP were obtained, such as operating voltage of 1000V, sputtering pressure of (4～5)×10-2Pa and deposition rate of 0.5nm/min. The results show that the ion-feedback barrier film deposited under this optimal conditions can meet the uniformity, compactness and less pinhole requirements.