Using modern information technology and artificial intelligence to achieve the condition based maintenance and predictive maintenance is one of the important ways to reduce the production cost in the process industries. The real-time monitoring network and artificial intelligent diagnosis technology for mechanical-electric plant was outlined in this paper. The Ethernet and FDDI based real-time monitoring network developed for compressors and pumps in petrochemical plants was introduced briefly. The black-gray-white gathering diagnosis method was given for the first time on the bases of approach to fault mechanism and distinctive symptoms. The mechanical fault diagnosis expert system based on black-gray-white gathering distinguishing sieve method developed in this work yields satisfactory results in the engineering practice.