Amphiphilic diblock copolymers, poly(methyl methacrylate)-b-poly (acrylic acid) (PMMA-b-PAA) was prepared by 1,1-diphenylethene (DPE) method. First, free radical polymerization of methyl methacrylate was carried out with AIBN as initiator in the presence of DPE, giving a DPE-containing PMMA precursor with controlled molecular weight. Amphiphilic diblock copolymer PMMA-b-PAA was then prepared by radical polymerization of acrylic acid (AA) in the presence of PMMA precursor. The formation of PMMA-b-PAA was confirmed by H-1 NMR spectrum and gel permeation chromatography. Transmission electron microscopy and dynamic light scattering were used to detect the self-assembly behavior of the amphiphilic diblock polymers in methanol.