An embodiment of the invention discloses a comparison standard device for standard voltage transformer on-site self-checking, and a checking method of the comparison standard device. The comparison standard device comprises a test power supply, an iron core assembly, a test power supply connection module and a disconnecting switch, wherein the test power source is electrically connected with the test power supply connection module, the disconnecting switch is electrically connected with a switching control power supply, and the test power supply connection module is fixedly connected with the iron core assembly after the disconnecting switch is switched on. The comparison standard device controls the disconnecting switch so as to control the switching on and off of the comparison standard device in a transformer self-checking system, and can regard a standard voltage transformer in the transformer self-checking system as a tested piece for checking and verification.