Using the ratio bridge circuit to detect the ratio of power transformers, the operation process is relatively cumbersome, and the detection range is narrow, which is not suitable for the fast-paced and high-speed requirements of modern detection. Therefore, the price of the power transformer grade measuring instrument adopts modern electronic information technology, and a new generation of fully automatic transformation ratio grade measuring instrument has been developed. This instrument is an ideal testing instrument for the electric power industry sector. It has the advantages of small size, light weight, high precision, and good stability. It uses large-screen LCD display with Chinese characters display and menus for operation. The operation interface is friendly, and the transformation ratio level can be tested at one time.