The invention discloses a fast-curing powder coating and a preparation method thereof, and belongs to the field of powder coatings. According to the invention, carboxylated polyester resin and triglycidyl isocyanurate are added for cross-linking reaction to form a network structure. The curing accelerator can activate carboxyl functional groups and effectively promote the functional groups in the carboxylated polyester resin to react, so that the curing speed of the powder coating is increased; the added precipitated barium sulfate can reduce the overall viscosity of the powder system; the modified leveling agent and the wetting accelerant have a synergistic effect, so that the wettability of the powder coating is effectively improved, the internal surface tension of the powder coating in the curing and melting process is reduced, the leveling performance of the powder coating is improved, meanwhile, the carboxylated polyester resin is easier to infiltrate pigments, volatile substances are accelerated to overflow from the surface, and the color fastness of the powder coating is improved. Meanwhile, under the synergistic effect of the degassing agent, bubbles are accelerated to break and overflow, the appearance of a coating film is obviously improved, a flat coating film surface is obtained, and therefore the problem that the coating film surface is rough and uneven due to rapid curing is solved.