The invention discloses a flexible alternating current/direct current electronic transformer checking device based on mixed sampling. The flexible alternating current/direct current electronic transformer checking device comprises a primary rising current circuit, a high-precision alternating current AD acquisition circuit, a high-precision direct current AD acquisition circuit, a standard transformer, an I/U converter, a main-control CPU module and a digital value acquisition module; an electronic transformer body to be checked is connected in series with the standard transformer and the primary rising current circuit sequentially through an optical fiber; the standard transformer is connected with the high-precision alternating current AD acquisition circuit; the primary rising current circuit is connected with the high-precision direct current AD acquisition circuit; the high-precision alternating current AD acquisition circuit and the high-precision direct current AD acquisition circuit are connected with the main-control CPU module; a merging unit is connected with the main-control CPU module through the digital value acquisition module; the main-control CPU module also sends synchronous signals to the high-precision alternating current AD acquisition circuit and the digital value acquisition module. Through the adoption of the device, alternating current and direct current checking of the transformer in a UPFC can be realized, the use is convenient, and the application prospect is excellent.