The ultrasonic attenuation Δα has been measured during the fatigue process of aluminium which is controlled by the total strain with a triangular or a sinusoidal waveform.The results indicate that the waveform has an influence on the Δα-ε curve at low strain amplitude,but has little influence at high strain amplitude.At low strain amplitude,the major reason causing the variation of Δα is the interaction between dislocations and point defects,and the waveform can change the re-distribution of point defects at the average stress field of the vibrating dislocation segments,as a result,the stable Δα-ε curves for the two kinds of waveform are different.At high strain amplitude,dislocation multiplication occurs,the interaction between dislocation segments is dominant,and the waveform cannot influence the dislocation multiplication and the interaction between dislocation segments.