The invention discloses a transformer direct-current resistance and no-load voltage ratio testing device. The testing device comprises a direct-current testing power source, a direct-current sampling unit, an alternating-current testing power source, an alternating-current sampling unit, a logic switching unit and a central processing unit, wherein the direct-current testing power source and the direct-current sampling unit are used for conducting direct-current resistance testing, and the alternating-current testing power source and the alternating-current sampling unit are used for conducting no-load voltage ratio testing. The central processing unit conducts switching between the two testing power sources and switching between the two sampling units according to operation commands of a tester through the logic switching unit, and transformer direct-current resistance and no-load voltage ratio testing is accordingly completed. Transformer direct-current resistance and no-load voltage ratio testing can be completed through one-time connection between the device and a transformer, and therefore the detection efficiency of the transformer is improved.