Abstract: Air data expert system of aircraft is a computer system applied for processing air data in a deep layer.In this paper,the structure mode,deducing mechanism and realization method of the expert system is introduced.The expert system utilizes distributed structure mode and mechanism of fuzzy reasoning with weights.The software of the expert system is realized by LISP language,while the hardware of the expert system is realized by multi-processor network.Finally,the importance and key problems of this study are given.