The invention relates to double-component polyurethane waterproofing paint and a preparation method thereof. The waterproofing paint consists of a component A and a component B, wherein the mass proportion of component A to component B is 1:3; the component A comprises polyoxypropylene ether polyol with a molecular weight of 1500-2500 and a functionality of 2, polyoxypropylene ether polyol with a molecular weight of 3000-5000 and a functionality of 3, 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate and chlorcosane; and the component B comprises vacuum distillate 4 line oil, the chlorcosane, dibutyl phthalate, methine di-ortho-chloro aniline (MOCA), talcum powder, ground calcium carbonate, kaolin, inorganic pigment, a high-boiling-point non-toxic aromatic hydrocarbon solvent, a T-12 catalyst and triethylamine. The preparation method has the beneficial effects that nontoxic diphenylmethane diisocyanate is used instead of virulent toluene diisocynate; and in addition, toxic raw materials such as coal tar, toluene, dimehtylbenzene and the like are not added any more. Thus, the paint and preparation method are beneficial to environment protection.