Abstract: The 50Mn2V steel supplied by a steel-making plant for saw blade matrix had poor hardenability, such as non-uniform hardness and large deformation, after being quenched. The reason of bad hardenability for the 50Mn2V steel was analysed by chemical composition analysis and microstructure observation. The results show that the bad hardenability of the 50Mn2V steel was because of the microstructure defects in the supplying sheets including obvious banded microstructure, net ferrite and bulky pearlite microstructure, and the defects were resulted from the abnormal continous casting process. The hardenability of the 50Mn2V steel could be improved by optimizing the corresponding continous casting parameters, such as liquid super-heating extent, the secondary cooling degree and the uniformity of cooling water.