The invention relates to a SiC-based diluted magnetic semiconductor thin film and a preparation method thereof. The method comprises the following step of irradiating a SiC thin film material with a certain dosage of carbon particles <12>C<+>, thereby preparing the SiC-based diluted magnetic semiconductor thin film. The SiC thin film after being processed according to the method has obvious room-temperature ferromagnetism, is relatively high in saturation magnetization, and has favorable potential application value. The method is stable and effective, and the SiC-based diluted magnetic semiconductor thin film material can be prepared on the premise of no damage to the material.