Abstract: As the core equipment for fast and reliable isolation of substation bus fault, bus bar protection is the focus of operation and maintenance inspection, maintenance and transformation. Firstly, the causes and positioning methods of differential current abnormality of bus bar protection are expounded. Then, the two problems of differential current abnormality of bus bar protection in 220 kV substation are analyzed and processed. Finally, the corresponding preventive measures are proposed, which provide solutions for the operation and inspection personnel to locate and deal with similar defects quickly and accurately.