With respect to human reliability of plant operation in nuclear power plant (NPP), a human model of NPP operator was developed as a computer simulation model which describes complex human cognitive behavior dealing with anomaly detection and root cause identification by monitoring presented information on CRT-based man-machine interface (MMI).First, the fundamental parameters for human reliability analysis (HRA) in NPP are summarized based on literature surveys and the meaning of human cognitive reliability (HCR) curve is described. Then, a small scale laboratory experiment was conducted to deduce HCR curves experimentally, and the experimental data and observation were utilized for constructing human model for operator¡Çs cognitive behavior to diagnose plant anomaly at MMI, where the modeling was largely based on Reason¡Çs memory model framework. By comparing HCR curve deduced from the laboratory experimental data with the one deduced by the human model simulation, the results show that the HCR curves deduced by the human model simulation agree well with the ones deduced by the laboratory experimental data.