The experiment for poly (vinyl chloride) suspension polymerization was performed in a small reactor with the volume of 0.005 m(3) and pilot scale reactor with the volume of 0.28 m(3), respectively. The influence of the physical properties of PVA (poly vinyl alcohol) suspending agents on the mean particle size of PVC resin was investigated in the small reactor and effect of agitation power on the mean size of PVC resin was examined in the pilot plant reactor. The mean particle diameter of PVC resin decreased with increasing solution viscosity of PVA suspending agent and increased with increasing interfacial tension between continuous and dispersed phases. For the concentration of suspending agents used, it decreased at the initial stage and then increased above the critical point. The mean particle diameters of PVC resin have been correlated with the physical properties of PVA suspending agent in a small reactor. And then, the mean particle diameters of PVC resin have been correlated with the energy dissipation rate per unit volume and the physical properties of PVA suspending agents.