Abstract: Terahertz wave has wave-particle dualism,good penetrability,low-energy,fingerprint,transient,water absorption,therefore it has been widely applied in many fields,such as material,national defense,physic,biology,microelectronics,agriculture,imaging,information technology. The feature and detection principles of terahertz wave,imaging technology,as well as the detection modes of terahertz transmitted wave and reflected wave are described. The application of terahertz wave in transformer insulating oil detection,moisture content detection of insulating oil,aging analysis of transformer insulating oil paper,moisture content detection of insulating pressboard,non-destructive detection of power equipment and thickness measurement of insulating materials in power industry are comprehensively described. Therefore,terahertz can be used as an important supplementary detection technology of power detection technology.