The rule of the effect of steel hardness on magnetiC barkhaasen noise(MBN) measurement parameter has been investigated. An empiric formula expressing relation between the hardness and the measurement parameter ET and Nis found out. The coeffieients which can be worked out through linear regressionmethod or graphic method. It is significant to find out such a relation to the quantitative measurement Of residual stress and the praCtice of MBN measurement technique.