Abstract: The correlation between 300M steel surface stress and Barkhausen signal has been studied by applying four points bending and analyzed with the magnetostrictive model. It has been shown that, when the direction of stress parallels magnetizing direction, Barkhausen signal increases with the increasing of tensile stress, decreases with the increasing of compressive stress. But at the same time, it has been found that the correlation changes when magnetizing direction deviates from the direction of stress, or magnetizing strength increases, even a contrary trend will advent in a special situation.