With the presence of industry 4.0 and China’s manufacturing 2025 plan, digital transformation and reform is growing vigorously in the process industry. However, the traditional maintenance modes couldn’t satisfy the equipment management requirements of process industry in the new digital ecology. This paper is based on cloud computation, edge computation, IOT, big data, mobile net and AI technology, the steel industry was taken as example, the intelligent maintenance of steel industry is defined and the total architectural framework of intelligent maintenance is designed. Besides, the edge’s monitoring alarm system, PHM system and industrial analysis algorithm also are developed, which are the key technology of intelligent maintenance in steel industry. Moreover, based on those key technology, centered on requirements of steel industry’s production line and critical equipment, combined with industrial mechanism models and experts’ experience, a series of intelligent maintenance systems of steel industry are developed, such as intelligent blast furnace, intelligent TRT, intelligent hot roll, intelligent cold roll, intelligent wire rod and intelligent maintenance knowledge graph. Finally, taken the intelligent TRT and intelligent rod wire as the typical examples, the practical application effectiveness of those systems in a steel group are briefly introduced, which verifies the feasibility and reliability of intelligent maintenance and provides the basis for digital transformation and equipment management reform in steel industry.