An on line defect inspection system of film was developed in our laboratory,which runs in high speed of maximum 60 m/min.The infrared images are obtained with a high quality and high speed CCD camera and processed in real time,by means of such algorithm as low pass filtering,edge detection and projection,etc.Experimental results show that accuracy rate of the system is upwards of 98 %,and that the system can inspect defects with the size of greater than or equal to 1 mm,and defects with the size of less than 1 mm if it has enough contrast to background.