Abstract: The nonlinear ultrasonic mixing method can be used for the micro-crack detection and localization research due to its high sensitivity to early micro-damage. Because the ultrasonic wave attenuates during propagation, the micro-crack detection based on acoustic nonlinearity coefficients usually has a certain deviation. In this paper, a method of nonlinear ultrasonic mixing method combined with attenuation compensation is proposed and adopted to detect micro-cracks in metal materials. The experimental research is conducted for the specimens of 4333M4 steel, and two shear waves are used to generate the sum-frequency longitudinal wave. In consideration of wave attenuation and the nonlinear mixing wave propagation, the two primary waves and the mixing wave are compensated for their corresponding attenuations to correct the acoustic nonlinearity coefficients. Specimens with micro-cracks of different lengths are prepared and scanned in the depth direction. By comparing and analyzing the change of the acoustic nonlinearity coefficients with and without attenuation compensation, it is found that the acoustic nonlinearity coefficients with attenuation compensation is more accurate in measuring the micro-crack length. And the detection results of two different primary frequencies with the same frequency ratio are relatively well consistent, the universality of this method is demonstrated. The results show that the nonlinear ultrasonic mixing method with attenuation compensation can accurately detect micro-cracks and measure the length. This research provides a more accurate method for the micro-cracks detection.