To obtain the polymer with good ageing property and the application in medium- and low-permeability oil layers, the water-soluble hydrophobically acrylamide-modified terpolymer (PAAN) with sodium 2-acrylamido-2-methylpropane sulphonate (NaAMPS) and 2-vinylnaphthalene as a hydrophobic monomer (VN) was synthesized by the micellar copolymerization. The differential scanning calorimetry (DSC) and thermogravimetry (TG) results show that large aromatic groups are incorporated into the PAAN polymer in the form of microblock structure and can increase the rigidity of molecular chains, resulting in the good thermal property of the polymer. The measurement results for intrinsic viscosities of PAAN indicate that the molecular weights of polymers are low and the breakage of the polymer chains can not occur at high shear rate. The polymer exhibits salt-thickening, temperature-thickening, thixotropy and good anti-ageing property. The hydrophobic microdomains and associating three-dimensional networks in the aqueous solution of PAAN were observed respectively by flourescent probe and ESEM.