Abstract: Cognitive reliability and error analysis method (CREAM) is a representative method of the socalled second generation human reliability analysis (HRA) method and can be used in both retrospective and prospective analysis. Not only the general CREAM was descried, but also using the context effect factor β and common performance condition (CPC) factor, the formula was obtained for calculation of cognitive error probability in probability safety assessment （PSA）/HRA of nuclear power plant and to provide a simplified CREAM quantification process. One example was provided in the steam generator tube rupture (SGTR) event of Qinshan Ⅰ Nuclear Power Plant. The results give a more validated information for future application of PSA/HRA.