A novel framework of human-computer-interaction for computer aided instruction (CAI) system is presented which aims at introducing a new off-the-job training environment to master nulear power plant monitoring skill by more user-friendly manner than by present. The framework is based on the following two new ideas; one is mutual adaptive interface (MADI) concept, and the other is virtual reality (VR). In order to realize a hardware mechanism of mutual adaptive interface based on VR, a new head-mounted-display (HMD) was developed which can not only provide the user with virtual environment conventionally but also detect the user¡Çs eyes images for in-situ analysis of various ocular information. The information are expected to utilize for realizing advanced human-computer-interaction in the CAI system.