For the requirement of the department for aviation accident investigation, a computer information system of processing the broken tape of flight data recorder has been designed. The main principles of the system are that magnetic track images are first preprocessed using image processing techniques, furthermore, the position coordinates of tracks are obtained using image recognizing techniques, finally, the data corresponding to track coordinates are obtained by encoding the track coordinates using the serial-parallel scanning method that is specially designed. The accurate ratio of automatic encoding is 99.3%. The times of automatic encoding are reduced to proximate 5 seconds from about 4 hours of two operators for one frame track image. This system is significant for aviation accident investigations.