Taking variable-section rotating cracked beam as an example, the damage identification based on auxiliary mass method combined with fractal dimension theory. Firstly, the mass-crack beam model is established, and the natural frequency curve is calculated with the mass position changing. Then the fractal dimension curve of natural frequency curve is obtained by using fractal dimension method, and the location and depth of the crack can be detected. Futhermore, the effects of crack position, crack depth, auxiliary mass and rotating speed are investigated in detail. The simulation results demonstrate the efficiency and accuracy of the proposed method.