The coarsening process of the droplets in two-phase polymer blend system was studied under 2-dimensional conditions using a phase contrast microscope and computer image analyzer.It was found that the substrate (glass) has significant effect on the phase separation and droplets coarsening process.The interfacial interaction(wetting effects)will accelerate the droplets coarsening process when one phase has stronger affinity to the substrate than another phase,and the growth of the droplets radius with time follows r3～taa>1. On the other hand,when there is almost the same interaction between the dispersed phase and the matrix with the substrate,i.e. the two phases have the same wettability to the substrate (such as the system of PP/PE),no effect of the substrate on the coarsening process of the droplets was observed,i.e.the growth law is r3～t according to Ostwald ripening theory. It is expected that there is a critical value for the interfacial tension between the components of blends under 2-D condition.The growth law of the dispersed phase changes-over above or below the critical point.