A hydrophobically associating polyacrylamide was synthesized using AM,AA,C16DM as monomers.The suitable reaction conditions were :w(initiator)=0.3%(based on the total monomers), x(C16DM)=0.5%,x(AA)= 25%，w(total monomers)=20%,pH7~8,reaction temperature 50℃,reaction time 8h,respectively.The structure was characterized by means of elemental analysis and infrared spectrum.At the same time,the results show that,the surface tension of the solution could be reduced to 42.2mN/m,when the mass concentration was 1g/L.The critical associating concentration appeared when the mass concentration was close to 3g/L.The viscosity declined slowly with temperature rose,and the solution had shear thinning.