The invention belongs to the study field of external insulation test of a power transmission circuit, and particularly relates to a pollution flashover testing method of insulator simulated RTV (room temperature vulcanization) coating dropping. The method includes steps of firstly evenly coating RTV coating at the surface of an insulator by a spray gun, and placing for 48-72 hours; then selecting a simulative dropping point at the surface, slightly scratching a small circle at the surface of the RTV coating coated by the dropping point through a small knife, and removing the RTV small circular slice to make the ceramic (or glass) material of the part expose outside; through controlling area of the small circles and interval of small circles, simulating different dropping degree; at last, performing artificial pollution test on the insulator after completing above treatments in an artificial fog room. The invention can simulate the aging degree and the pollution resistance of the insulator operated on line, exactly judge the withstand voltage level and service life, and timely replace the insulator which has been reached the extreme of life, and prevent the pollution flashover phenomenon.