A new type of quaternary ammonium surface‐active polymer for enhanced oil‐recovery application was synthesized through the free‐radical polymerization of a functional monomer (DMCA) with acrylic acid (AA) and acrylamide (AM) and denoted as AM/AMPS/DMCA. The optimum polymerization conditions of AM/AMPS/DMCA were explored, and its chemical structure was characterized by Fourier transform infrared spectroscopy, hydrogen nuclear magnetic resonance, and environmental scanning electron microscopy. The molecular weight of AM/AMPS/DMCA was determined by gel‐permeation chromatography. Its thickening ability, oil–water interfacial tension, and emulsifying property were investigated. Results showed that AM/AMPS/DMCA had superior thickening ability and lower interfacial tension than the binary polymer AM/AMPS, as well as good emulsifying properties. AM/AMPS/DMCA also yielded 26.00% oil recovery, higher than the 20.57% of AM/AMPS, as determined using polymer‐flooding tests. The oil‐displacement mechanisms of this surface‐active polymer at pore level were also explored. Analysis of microscopic displacement characteristics through a visual micromodel revealed that AM/AMPS/DMCA solution improved sweep efficiency and reduced residual‐oil saturation due to its bulk viscosity and surface activation. All these findings indicated the excellent potential of AM/AMPS/DMCA in oil displacement.