The invention relates to a method for preparing a carbon fiber with a silicon carbide coating on the surface. The method includes: heating a carbon fiber for pretreatment, and then cooling the carbonfiber to room temperature; evenly mixing SiC powder with silicone rubber according to the mass ratio of (5-10):100 to obtain mixed sizing agent; fully mixing the carbon fiber with the mixed sizing agent according to the mass ratio of (3-5):100; heating the carbon fiber fully impregnated with the sizing agent to 400-600 DEG C to perform reaction for 1-2 hours, and then cooling to room temperature to obtain the carbon fiber with the silicon carbide coating on the surface. Compared with the prior art, the method has the advantages that carbon fiber damage is avoided, special equipment, high temperature and special gas are not needed in the preparation process, the preparation process is greatly simplified, and the preparation cost is greatly reduced.