We have developed new types of plant-maintenance training systems by using virtual reality (VR). One is the training system for disassembling a check- valve, and the other is that for detecting the failure part in the logic card of the control-rod driving-mechanism control system. VR-based training system is expected to have salient features as an experience-oriented CAI system, and these two training simulation systems showed its promising applicability in the area of plant maintenance. In this paper, the functions necessary for the VR- based experience-oriented training system are first discussed, and then explained is the way how they were realized in the two training systems we developed. The future developmental works are also discussed, for realizing the effective training simulation system.