Dynamic mechanical loss spectra correspornding to different frequency were measured at ascending temperature for amorphous polymer PVC (a-PVC). It is found that measuring frequency dependance of the parameters of a-peak obviously exists. To determine the contribution of τ0 or ΔH distribution to τ distribution, on the basis of analysing relaxation time distribution (τ distribution) of α-peak in a-PVC, the parameters of τ0 and ΔH have been calculated in this paper.