The invention discloses a functional polymer with surface activity and a preparation method for the functional polymer and an application of the functional polymer. The functional polymer with surface activity comprises a structural unit A, a structural unit B and a structural unit C, wherein the structural unit A is a structural unit with a structure represented by a formula (1), the structural unit B is a structural unit with a structure represented by a formula (2), and the structural unit C is a structural unit with a structure represented by a formula (3), and the viscosity average molecular weight of the functional polymer with surface activity is 5000-13000 thousand. The polymer has good surface activity, capacity of thickening a water medium and good temperature-resistant and salt-resistant capacity and aging resistance. The polymer oil-displacing agent is suitable for medium-low permeability reservoirs and high-temperature high-salt reservoirs, and can further enhance the oil recovery in tertiary oil recovery.