Abstract: C.I.Pigment Blue 15∶1 was encapsuled by miniemulsion polymerization with styrene and butyl acrylate for the purpose of improving the rubbing fastness and reducing the use of auxiliaries such as binders.The effects of the amount of surfactants and monomers on the average particle sizes,PDI,stability of the system were investigated.The morphologies of the ultrafine particles were observed by the scanning probe microscope.The results indicated that the average particle size of the pigment first increases and then decreases as the amount of the monomers increases;the amount of surfactant affects the average particle sizes and the stability of the system;the rubbing fastnesses of the modified pigment for pure cotton fabric is rather good with absence of binders.