The object of this study was to prepare poly(MMA / BA) latex by miniemulsion polymerization. Water insoluble dye (Blue 70) is added in the reaction mixture to investigate the nucleation mechanism during the polymerization. In addition, conversion, fractional conversion, DSC, colloid diameter and zeta potential data were used to investigate the relationship between monomers and particle nucleation mechanism. Besides, Ostwald ripening effect, creaming line and phase separation were used to discuss monomer droplet stability. It is found that empirical equation would be used to calculate Ostwald ripening rate in three-component system.