The predictive maintenance within the framework of intelligent-control-maintenance-management system (ICMMS) makes full use of all the information of control, maintenance, and technical management aspects to make right maintenance at the right time in the right place. In this paper, the three key elements of the predictive maintenance within the framework of ICMMS are presented. The ICMMS platform for hydroelectric generating unit, especially its maintenance function, is introduced. An artificial-neural-network (ANN)-based identification and diagnosis model is set up to implement the predictive maintenance of the electrohydraulic servomechanism in the hydroelectric generating unit. The tests show that the proposed strategy can guarantee ideal performance.