The invention belongs to the technical field of electrical engineering, and particularly relates to an expected TRV detection device and method for a high-capacity test system. The device is characterized in that a high-capacity test system power supply is connected with a power supply side adjustable reactor, the other end of the power supply side adjustable reactor is connected with a tested switch device, the other end of the tested switch device is connected with a load adjustable reactor, and the other end of the load adjustable reactor is grounded; a power supply side frequency modulation branch is connected with the power supply side adjustable reactor; a load side frequency modulation branch is connected with the load side adjustable reactor; a TRV measurement system is connected with the tested switch device, and the other end of the TRV measurement system is connected with a signal of a central processing unit; the other end of the signal of the central processing unit is connected with a frequency modulation branch control system, and the other end of the frequency modulation branch control system is respectively connected with the power supply side frequency modulationbranch and the load side frequency modulation branch. The expected TRV detection device and method is simple in structure and reasonable in design, reduces system electric energy and equipment loss and has few interference signals, and the accuracy of detecting TRV waveform is high.