In this paper, a fuzzy synthetic decision-making system which is based on the method of debris group analysis for wear condition monitoring and fault diagnosis in qualitative ferrographic analysis and the background to establish it have been introduced. Especially, the procedure to find out the membership functions of this fuzzy synthetic decision-making system and the method to arrange the importance sequence of severe wear particles have been explained in detail. The reliability of this fuzzy system has been tested by actual practices of wear condition monitoring and fault diagnosis, and the possibility to realize automation in ferrgraphic analysis has also been revealed.