The invention discloses toughening coating and a preparation method thereof and belongs to the technical field of processing of chemical coatings. The toughening coating is prepared by dissolving in a solvent, by weight, 100-120 parts of epoxy resin, 20-30 parts of isocyanate-terminated unsaturated polyester solution, 10-20 parts of filling material, 15-20 parts of glass flakes, 5-20 parts of a pigment, 10-20 parts of an acid anhydride curing agent, 0.5-1 part of dibenzoyl peroxide, 0.5-1 part of N,N-dimethylaniline, and 0.05-0.1 part of an accelerant. The isocyanate-terminated unsaturated polyester modifier having excellent toughness is prepared, dibenzoyl peroxide and the epoxy curing agent are added, the surface of the glass flakes is treated, the glass flakes are then added to coating, and the prepared coating may be cured fast at low temperature; a cured coating layer has good adhesive property and toughness and rarely cracks or sheds in long-term usage in the environment with frequently varying temperature and humidity.