The invention discloses an acrylamide copolymer, and a preparation method and application thereof, belonging to the field of the petrochemical industry. The acrylamide copolymer contains a structuralunit A, a structural unit B and a structural unit C, wherein the structural unit A is a unit with a structure as shown in a formula (1) that is described in the specification; the structural unit B isat least one selected from units respectively with structures as shown in formulas (2)-formula (7) that are described in the specification; the structural unit C is a unit with a structure as shown in a formula (8) that is described in the specification; a weight ratio of the three structural units is 1: (0.001-10): (0.001-10); and the acrylamide copolymer has a viscosity average molecular weightof 1 million to 40 million. The copolymer of the invention has good water solubility and low residual monomer content; and in particular, under the conditions of high temperature and high salt, the apparent viscosity, thickening properties and oil dispersing ability of the solution of the copolymer are greatly improved compared with conventional polyacrylamide.