The invention discloses a detection method for disconnection of voltage transformers. Two voltage transformers are applied to generator protection in a pumped-storage power station, and include a first voltage transformer in a power generation direction and a second voltage transformer in a pumping direction. The detection method for disconnection of the voltage transformers comprises the following steps of: collecting voltage signals from the first and second voltage transformers; working out voltages U1AB, U1BC, U1CA, U2AB, U2BC and U2CA; working out voltage amplitude differences of lines of the two voltage transformers [delta]UAB, [delta]UBC and [delta]UCA, and judging whether the voltage transformers are in disconnection. The detection method can be applied to various connection modes at the generator end of the pumped-storage power station, and is simplified in detection on disconnection of the voltage transformers in various connection modes, wide in application range, high in reliability, and convenient to implement general microcomputer protection.