Abstract: The analysis of causes and influencing factors of hardness non- uniform in the 65 Mn saw blades with hot rolled steel had been performed by means of hardness,optical microscopy,SEM and EDS. The result shows that tnon- uniform hardness of 65 Mn hot rolled steel is caused by non- uniform spacing of pearlite lamellar,the existence of banded structure and decarburization. uneven spacing of pearlite lamellar is main factor whose feature are large difference in pearlite spacing sizes and poor straightness of its structure. After optimizing cooling process after final rolling,steelmaking process,continuous casting and heating system,the surface hardness uniformity of 65 Mn hot rolled steel was improved effectively.