Hydrophobically associating polyacrylamide (PAMBA) modified with long fatly chain prepared by free radical polymerization of octadecyl acrylate (ODA), acrylamide (AM), 2-acrylamido-2-methyl propane sulfonic acid (AMPS) and acrylic acid (AA). The effect factors in the process of polymerization were discussed, and the optimum copolymerization conditions were determined, and the performances of PAMBA were characterized by infrared spectrum (FT-IR), X-ray diffraction (XRD) and transmission electron microscope (TEM). The results showed that the optimal reaction condition was obtained with the viscosity value as evaluation index, the monomer content of ODA, AMPS and AA was 0.6%, 20% and 10%, respectively, and the initiator dosage was 0.3%. At room temperature and shear rate of 170 l/s, the viscosity of the 0.2% PAMBA solution was 56.2 mPa·s. There were strongly intermolecular hydrophobically associating interactions in the PAMBA aqueous solution.