Abstract: The applications of the defense in depth in the design of the irradiated fuel water pool storage, I&C system, electrical system, and the protection systems for internal and external hazards of the nuclear power plant are reviewed in this paper. Base on the study of the newest standard and codes, the design requirements of each level of defense in depth in the above systems are confirmed. The analysis of the design features for the defense in depth in an advanced nuclear power plant in China shows the application value of defense in depth in various fields.