In traditional digital holography,the measurement of amplitude of vibration is realized by detecting the intensity distribution of reconstructed image,and satisfied results can not be obtained.The phase of the first kind zero-order Bessel function has binary values,zero and π,thus,the distribution of amplitude of vibration can be measured through the phase of reconstructed wave.Theoretical analysis demonstrates that the phase change caused by the shift of illuminated light is ignored in discussion before.In this study,this method is corrected by overlapping a phase factor and a new method is put forward to eliminate the effects of this factor by utilizing the phase characteristics of squared Bessel function.Experiment shows that,this phase factor not only exist,but also influence final measurement.Using proposed method,this influence can be eliminated very well.Moreover,it will bring convenience into the measurement of amplitude of vibration via the phase of reconstructed wave in time-average digital holography.