The low-temperature impact fracture of controlled-rolled and normalized steel 09MnNb has been investigated. Data on the load-flexibilty plot after impact test at various temperatures show that the steel either controlled-rolled or normalized offers higher resistance to tearing. The fracture occurred below the ductilebrittle transition temperature is by cleavage with dimpled rupture. The controlledrolled steel has a mixed α-grain structure which consists of equiaxial α-grains and "cold-worked" elongated grains with higher dislocation density, while the normalized steel has finer equiaxial α-grains with cell substructure of dislocation, of which the effective size of a-grain may be reduced. This microstructure of normalized steel makes the improved low-temperature impact property possible.