The characteristics of the valve side of rectifying transformer are analyzed, and the measurement method of the valve side high current collection of the rectifying transformer is proposed. The valve side high current collection of the rectifier transformers is completed by using special shaped electronic current transformer, current collector, and merging unit. The collection problems of low voltage side current of the rectifier transformer are solved, recording data of the valve side current is analyzed, and the differential protection scheme for the differential protection is made possible, state monitoring of the valve side can be realized. To provide evidence for regulating rectifier units in metallurgical industry and chemical industry.