A simple method for charaeterizing polymer molecular weight distribution by three parameters，Vp，(V10—Vp)，(Vp—V90)，from the gel permeation chromatogram is pro-posed． Vp being the peak elution volume of differential GPC curve charactrizes the average molecular weight of the polymer．(V10—Vp) and (Vp—V90)，where V10，V90 being elution volumes at 10％ and 90％ cumulative weight of the integral GPC curve，characterize the breadth of the GPC curve emphasizing ttle extent of the low (high elution volume) and high (low elution volume) molecular weight ends of the distribu．tion．The low and high molecular ends of the distribution usually play an important role in the effect of molecular weight distribution on the processing ctmracteristics of the polymer and mechanical properties of the fabricated article．Application of this method to the ease of polycarbonate shows that these three parameters can well characterize the differences in the GPC curves of several samples and to give good correlation with the diffeFences in the mechanical properties such as impact strength and environment stress cracking of the extruded bar specimens．