Abstract: Based on the human error analysis theory and the characteristics of maintenance in a nuclear power plant, human factors of maintenance in NPP are divided into three different areas: human, technology, and organization, in which human refers to the individual factors, mainly including psychological quality, physiological characteristic, state of health, knowledge, skill level, and interpersonal relationship. Technology includes the maintenance technology, maintenance strategy, maintenance tool, maintenance interface, maintenance regulation, and work environment. Organization includes task arrangement, information communication, training, personnel external environment, team construction, and leadership. The analysis also reveals that the organization factors, which can indirectly influence personnel performance, are the primary initiators of human error. Based on these, some countermeasures are brought forward in order to reduce human errors.