Abstract: The abnormal structure at the edge sealing ring of HRB500 aE steel bar was the harmful structure in the steel bar, which affected the quality and use of the steel bar. In order to ensure the quality of steel bar, combined with the steel bar products under three different production processes, the microstructure, properties and chemical composition of the steel bar were comprehensively tested and analyzed by using the automatic steel bar tensile test system, optical microscope, Vickers hardness tester and direct reading spectrometer. The abnormal microstructure type at the edge sealing ring of the steel bar was determined, and the causes were analyzed. The results show that there were three kinds of abnormal structures at the edge closed ring of HRB500 aE steel bar, which were tempered martensite, bainite and widmanstatten structure. It was recommended to use the third process method to produce steel bars. The results could provide support for the adjustment of rolling process parameters and avoid unqualified steel products.