The DC resistance of the transformer is a must-test item for semi-finished products, finished products factory testing, installation, handover testing and preventive testing of the power department in the manufacturing of transformers. It can effectively detect manufacturing defects such as material selection, welding, loose connections, missing strands, broken wires and other manufacturing defects of transformer coils, as well as hidden dangers after operation. In order to meet the needs of rapid measurement of DC resistance of transformers, the instrument adopts new power supply technology and has the characteristics of small size, light weight and large output current. The whole machine is controlled by a single-chip microcomputer, which automatically completes self-test, data processing, display and other functions, and has automatic discharge and discharge indication functions. The instrument has high testing accuracy and is easy to operate, and can quickly measure the direct resistance of the transformer.