Abstract: The reasons for the unqualified low temperature impact performance of large aspect ratio thin steel plate for bridges were studied using methods such as chemical composition analysis, fracture analysis, metallographic examination, and inclusion analysis. The results show that the central segregation of the slab, the formation of martensite during cooling after rolling, and the existence of coarse MnS inclusions in the steel led to unqualified low temperature impact properties of the steel plate. The methods to improve the low temperature impact performance of steel plates included reducing the content of elements such as C, Mn, P, and S during the steelmaking process, reducing the superheat of molten steel, and using strong cooling technology at the solidification end. During the steel rolling process, increasing the heating temperature, extending the heating time, optimizing the distribution of pass reduction, and reducing the final rolling temperature are necessary.