There are many auto-flight system modesin modern civil aircraft; they are interrelation and influence among these modes;and it is easy to cause mode confusion. To resolve the problem of mode confusion, this paper focuses on investigation about mode logic of automatic flight control system and summarizes the translation relationship of flight director, auto pilot, lateral modes and vertical modes. Utilizing Stateflow, we established the model of automatic flight control system functions; the simulated flight control panel &the display interface of automaticflight mode was set up by the tool of GUI in Matlab software;and theautomatic flight mode transition was simulated. Finally, the validity of the mode transition was verified by expected mode transition logic matrix.