The invention discloses a calibration device for an ultrahigh-frequency partial discharge online monitoring device in the field environment. The calibration device comprises a measured on-line monitoring device, a measured sensor, a measuring host, a signal generator and a measurement standard-based measuring module. The measured sensor is arranged on the measured on-line monitoring device. The measured sensor is connected with the measuring host. The measurement standard-based measuring module is connected with the measured sensor through a radio frequency cable. The signal generator is connected with the measured sensor and is used for injecting an ultrahigh-frequency electromagnetic wave signal into the measured sensor. The measuring host is used for acquiring the measured response signal of the measured on-line monitoring device. The measuring module is used for acquiring the standard response signal of the measured sensor. The measuring host is used for generating a calibration result according to the acquired standard response signal and the measured response signal. By adopting the calibration device of the invention, the calibration operation efficiency is improved, and the number of human errors is reduced. The confidence degree of calibration data is improved. The influence of factors such as distribution parameters, connection reliability degree and external interference introduced by the frequent introduction of connecting lines on tests is reduced.