Abstract: Portable equipment acts as necessary facilities for mitigating severe accidents, of which the accessing process are mostly complex in nuclear power plants. In order to analyze the reliability of nuclear power plant operators when operating portable equipment, this paper studies the characteristics of the implementation of improvement items added after Fukushima Nuclear Accident, proposes an assessment model based on Human Error Mode and Effect Analysis by defining human error probability, human error effects, human error recovery probability as risk factors, and combines experts evaluation with fuzzy linguistic theory. A case study of mobile power supply task under Station Black Out accident is given to get the importance ranking of human error modes as well as reasonable risk views, through which the feasibility of the model is verified.