The invention provides a verification system and method for an online monitoring device of onsite capacitive equipment, and the calibration system comprises a voltage sampling device, an FM (frequencymodulation) transmitting device, an FM receiving device, a human-machine interaction device, a current output wire, and a measurement sensor. The verification method comprises the steps: firstly obtaining a PT voltage signal corresponding to the onsite capacitive equipment as an operation reference voltage signal through the voltage sampling device; secondly modulating the operation reference voltage signal into a composite audio signal through the FM transmitting device, carrying out the frequency modulation transmission, transmitting the composite audio signal to the FM receiving device through wireless transmission, and outputting a reference current signal which has the same frequency as the PT reference voltage and has the programmable phase and amplitude after the demodulation, programmable amplitude and phase modulation and amplification; thirdly carrying out the parameter overlapping of the reference current signal and an initial current signal of the online monitoring device,and obtaining a current, a capacitance and a dielectric loss theoretical increment; fourthly injecting the reference current signal into the online monitoring device, and measuring the actual current, capacitance and dielectric loss increment through the online monitoring device; finally comparing the theoretical increment with the actual increment, and verifying whether the online monitoring device is qualified or not.