The invention relates to a virtual dielectric loss device and a detecting method thereof. The virtual dielectric loss device comprises a voltage proportion conversion module, a precise phase shifting module, a precise current amplifying module and a control module. The voltage proportion conversion module, the precise phase shifting module and the precise current amplifying module are connected in sequence, and the control module is respectively connected with the precise phase shifting module and the precise current amplifying module. The method comprises the steps that firstly, a high-voltage signal output from the high-voltage end of a dielectric loss tester to be detected is converted into a low-voltage signal; secondly, the converted voltage signal is processed through the phase shifting module to obtain a needed phase position; thirdly, the signal output through the phase shifting module is output to become a current signal amplified through the precise current amplifying module according to the demands; fourthly, the output current signal is input to the measuring end of the dielectric loss tester to be detected; fifthly, different dielectric loss factors are simulated through phase shifting, and different capacitances are simulated through current amplifying. The virtual dielectric loss device is fast and convenient to operate, and the dielectric loss tester is effectively detested/ corrected.