Polymer and its preparation method and application, and processing method for oily sewage

The invention provides a polymer and its preparation method and application, and a processing method for oily sewage. The structural unit of polymer is composed of a acrylic acid hydrophilic structural unit, a cation structural unit, and an acrylate hydrophobic structural unit, with content being (by weight percentage) 50-67, 30-48, and 2-10. Intrinsic viscosity of polymer is 33-362 mL/g. The preparation method of the polymer includes contacting acrylic acid hydrophilic structural unit, methacryloxyethyltrimethyl ammonium chloride and acrylate hydrophobic structural unit in existence of initiator. The polymer can be used in oily sewage treatment.