Abstract: A new idea is proposed for device fault diagnosis, the device faults were divided into the functional faults and constructional faults.Based on it, anovel approach of intelligent diagnosis was investigated.The diagnostic expert system based on Artificial Neural Networks(ANN)is developed for MK9-5 cigarette machine, and the tests were carried out in the laboratory.It has been shown that the new intelligent diagnostic expert system based on ANN has higher liability than the common diagnostic expert system.