A hydrophobic monomer was synthesized by using amino propyl intermediates dimethyl methyl acrylamide (DMAPMA) and 1-bromohexadecane. The new hydrophobically associating copolymer PAAD-16 has been prepared by aqueous solution polymerization , which can be used as an acid thicker and the monomers are acrylamide(AM), anionic monomer 2-acryamido-2-methylpropane sulfate acid (AMPS) and DHAB. And it had been characterized by means of IR, FL and SEM. Evaluated the performance of the PAAD-16, and the results show that the acid dissolving time of this thickener is about 90 min; the apparent viscosity of this viscous acid is 59mPa·s at 30 ℃ and 170 s-1; ω of this viscous acid was respectively 85.0% and 66.1% at 60 ℃ and 90 ℃. Under the conditions of 30 ℃, 170 s-1, ω' of this viscous acid is 81.4%, it has excellent viscosity increasing, temperature resistance, shear resistance and retarding performance. Key words: hydrophobic association; polymer; thickener;acid solution