In this research work, the micron size PMMA ( Poly Methylmethacrylate) polymer particles were prepared by dispersion polymeraization. In order to achieve optimum conditions, different concentration of initiator, monomer and dispersion medium were used. The polymer particle size distributions were then investigated by using light diffraction & laser technique. Variation in concentration of initiator showed that mean particle size decreased as the concentration of initiator AIBN (2, 2-Azobis Iso Butyro Nitrile) was increased. The particle size distribution became wider with increase in concentration of initiator. Monomer concentration increase shows increase in the particle size and broaden the size distribution. However, when monomer MMA (Methyl methacrylate) concentration was decreased the particle size also decreased whereas the particle size distribution is less wide as compared to concentration increased.