Monodispersed PMMA (polymethyl methacrylate) particles were prepared via a dispersion polymerization process using methanol as the dispersive medium, azobisisobutyronitrile (AIBN) as initiator, and polyvinylpyrrolidone (PVP) as steric stabilizer. This study applied the Taguchi experimental design to determine an optimized formulation for preparing monodispersed PMMA particles at a stabilizer molecular weight of 360kDa, a concentration of 8.0wt.%, a monomer concentration of 5.0wt.%, and an initiator concentration of 0.05wt.%. The addition of water to the dispersive medium alters the dispersive medium solvency, causing a reduction in size of the monodispersed particles, which could be as small as 0.40μm diameter under our experimental conditions. We used pure methanol as dispersive medium, and successfully prepared spherical monodispersed composite particles containing pigment green 36 and PMMA by dispersion polymerization in the presence of pigment green 36. The experimental results show that the arithmetic mean size of composite particles decreased, and pigment content in composite particles increased after increasing the amount of pigment in the polymerization process.