The invention discloses a medical pipe and a preparation method thereof. The preparation method of the medical pipe comprises the following steps: S1, obtaining a medical pipe; S2, placing the medicalpipe and an isocyanate solution in a reaction kettle, filling carbon dioxide into the reaction kettle, and adjusting the temperature and pressure in the reaction kettle to enable the carbon dioxide in the reaction kettle to be in a supercritical state to obtain a medical pipe with isocyanate groups after reaction; and S3, placing the medical pipe treated in the step S2 into a modified material solution for reaction to obtain the medical pipe modified by a coating. According to the invention, the reactive functional groups are introduced on the surface of the medical pipe by the method that the supercritical carbon dioxide carries isocyanate, so that the reactive functional groups can chemically react with functional groups in a modified material, the surface modification of the medical pipe is realized, and the biological performance of the medical pipe is improved.