Using variable ratio bridge to measure transformer's variable ratio, the operation process is tedious and the measurement range is narrow. It can't meet the requirement of fast rhythm and high efficiency of modern measurement. To this end, our company has developed a new generation of fully automatic variable ratio group tester using modern electronic technology. It has small volume, light weight, high precision and good stability. It uses large screen Chinese character display, menu operation, friendly interface. The change ratio group can be completed at one time. This instrument is an ideal test instrument for the electric power industry.