The invention discloses an aminolysis polymer, and a preparation method and application thereof, belonging to the field of preparation of high polymer materials. The preparation method of the aminolysis polymer comprises the following steps: (1) preparation of poly(maleic anhydride-high carbon methacrylate) intermediate product; (2) pulverization treatment of intermediate product; (3) preparation of aminolysis poly(maleic anhydride-high carbon methacrylate) pour-point depressant; and (4) treatment of target product aminolysis poly(maleic anhydride-high carbon methacrylate) pour-point depressant reaction solution and preparation of powder. The pour-point depressant has the advantages of favorable pour-point depression and visbreaking effects, low cost, simple production and clean and pollution-free process, and the product is easy to obtain, transport and store. The net pour-point depression amplitude for the Daqing high-wax thick oil is up to 8 DEG C, and the apparent visbreaking ratio is up to 72.1%, which are respectively better than the pour-point depression effects of the commercially available EVA (ethylene-vinyl acetate): the net pour-point depression temperature is 4 DEG C, and the apparent visbreaking ratio is 68.7%.