The invention discloses a testing device for the mutual inductor boundary dimensional identity. The testing device comprises a base, a positioning device, an ex-circle detection device, a base detection device and a controller, wherein the positioning device comprises two positioning pins and two first air cylinders; the first air cylinders are installed on the base through first brackets; conicalfixing blocks are arranged at the ends of piston rods of the first air cylinders; the base detection device comprises a supporting plate, a first spring and a first displacement sensor; through holesmatched with the positioning pins are formed in the supporting plate; the first spring is arranged between the supporting plate and the base, and the first displacement sensor is arranged on the base; a telescopic rod of the first displacement sensor is fixedly connected with the supporting plate, and the ex-circle detection device comprises a second displacement sensor; and the second displacement sensor is installed on the base, and the first air cylinders, the first displacement sensor and the second displacement sensor are correspondingly and electrically connected with the controller. The phenomena of mutual inductor dropping and verification data over-tolerance caused by difference of boundary dimensions in the verification process of a mutual inductor are effectively avoided.