The invention relates to a self-cleaning coating material for a car outer surface, which consists of the following components in parts by weight: 50-70 parts of methyl alcohol, 21-25 parts of water, 1-5 parts of stannic oxide, 1.0-1.5 parts of platinum, 0.5-1.0 part of tungsten oxide and 6-9 parts of silicon dioxide. The preparation method of the self-cleaning coating material for the car outer surface includes the following steps: S1, preparing materials; S2, preparing a solution; S3, mixing. Compared with the prior art, the invention has the following advantages: the coating obtained throughthe formula has the self-cleaning effect, is not easy to adhere dust, and cannot form water drops or water curtain on the surface after being scoured by water, water stains can be removed and the coating can be further brushed and cleaned, so that the car washing frequency is reduced, the living cost is reduced, and the benefit of environmental protection is improved; besides, high hardness and chemical resistance are achieved, the surface is still wear resistant when the car is in high-speed motion, as a result, the service life is prolonged, the car body resistance is effectively reduced, and the antistatic effect is achieved.