The invention relates to platinum vulcanization millable polyurethane and a preparation method thereof. The polyurethane is prepared from, by weight, 100 parts of polyurethane, 10-50 parts of filler,2-4 parts of hydrogen-containing silicone oil and 3-5 parts of a vulcanizing agent. The preparation method includes the steps that the filler and the polyurethane are evenly mixed in an internal mixer, the mixed polyurethane is taken, and the hydrogen-containing silicone oil and the vulcanizing agent are sequentially added onto an open rubber mixing mill in small amounts in multiple batches. Finally, a rubber compound is vulcanized on a flat rubber vulcanizing machine at the temperature of 150-190 DEG C for 5-15 min, and the platinum vulcanization millable polyurethane is obtained. The platinum vulcanization millable polyurethane has the advantages of being low in hardness, good in mechanical performance, high in safety and the like.