The invention belongs to the technical field of polyurethane and specifically relates to a preparation method of a polyurethane heating radiator. The preparation method of the polyurethane heating radiator comprises the following steps: uniformly mixing polyether polyol A and polyether polyol B, heating, dehydrating under high vacuum, cooling, adding diphenylmethane diisocyanate, uniformly stirring, heating and reacting, sampling and testing until mass content of isocyanate is 9-15% so as to obtain a prepolymer A component; uniformly mixing a chain extender and a tin catalyst to obtain a B component; uniformly mixing the A component and the B component, pouring the mixture into a mold, reacting to obtain a test piece, and vulcanizing the test piece to obtain a finished product. The prepared polyurethane heating radiator has good water resistance, is resistant to water seepage, is anti-rust, is not easy to block, has high hardness, is stretch-proof, is tear resistant, has high temperature resistance, will not deform, has stable physical properties, has more excellent heat dissipation performance than a metal product and is light. Production cost of the heating radiator is low. The preparation method is simple and easy to operate, and is easy to realize.