Abstract: In-service inspection is one of the important guarantees of safety operation in nuclear power plant. Human errors are the important inducement of in-service inspection failure. This article analyzed the reasons of human errors from three categories, which were human factor, technology factor and administration factor, respectively. Some countermeasures aiming to deal with these factors were put forward. This article considered that it should make human factor, technology factor and administration factor as a whole, and introduced the ethic of Planning, procedures, amendments, and excellent work, to reduce the human error events.