The interfacial tension on coarsening process of the polymer blend thin film on substrate was studied by using a phase contrast microscope and computer image analyzer．The ethylene vinyl acetate copolymers (EVAc) with different contents of VAc were blended with polyproplyene (PP)

and a series of PP／EVAc blends with differene interfacial tension was obtained．It was found that the coarsening process of the polymer blend 2D thin film on glass substrate was always accelerated when the interfacial tension is larger than a threshold value to be about 0.48·10-5 N／cm．When the interfacial tension of the blends is less than the threshold value

the coarsening process of the polymer blend thin film on glass substrate is as same as the bulk of the blend；i．e．no occurrence the phenomenon of the substrate induced coarsening process is．This result corresponds to our previous research results．Using substrates with various surface tensions

the coarsening processes of the polymer blend was found to be similar．In other words

the accelerated coarsening processes exist in all cases．The particle coarsening process only depends on the interfacial tension of the blend and the existing of the substrate

does not depend on the character of the substrate.