Abstract: It is identified in the fire probabilistic safety assessment (PSA) of nuclear power plants that human action has important effect on the risk of plant under fire condition. So it’s necessary to assess human error probability under fire condition by the systemic methodology. The HCR/ORE and CBDTM models and specific considerations under fire condition were described in this paper. The combination of HCR/ORE, CBDTM and THERP was applied to human reliability analysis (HRA) under fire condition with an example given for demonstration. The basement of setting up the more practical fire PSA models for engineering is established.