The invention relates to a formula and a preparation method of a one-component aromatic polyurea coating. The one-component aromatic polyurea coating is prepared from the following materials in partsby weight: 20-40 parts of aromatic isocyanate, 10-15 parts of polyester polyol, 5-10 parts of polyether polyol, 26-28 parts of polytetrahydrofuran polyether, 3-5 parts of butanediol, 10-15 parts of ketimine, 0.1-0.5 part of an organotin catalyst and 5-20 parts of solvent oil. The preparation method comprises the steps of enabling the ketimine, as a sealing agent, and an aromatic isocyanate-based prepolymer to coexist in the same reaction system, and isolating the system from air by using an inert gas or nitrogen; once the system is in contact with the air, eliminating the sealing of the ketimine under the action of water, so that the released terminal amino group (-NH2) rapidly reacts with -NCO so as to form the one-component aromatic polyurea. The one-component aromatic polyurea coating provided by the invention has higher mechanical properties and stable performance at a high temperature, and can adapt to a high temperature working environment of 100-140 DEG C. The process provided by the invention is simple, does not require large equipment, and is suitable for large-scale popularization and application.