The invention relates to the technical field of silicon carbide, in particular to silicon carbide ultrafine powder and a production method thereof, and the preparation raw material of the silicon carbide ultrafine powder is in-situ synthesized high-purity 6H-SiC micro-powder with a particle size of 2-5 mm. The production method comprises the following steps: carrying out ball milling on a siliconcarbide particle raw material; adding a foaming agent and mixed acid, carrying out a de-acidification treatment; carrying out magnetic separation by adopting a wet magnetic separator; adding a surfactant to react; carrying out microwave drying, and using an ultrasonic rocking sieve to perform screening so as to obtain silicon carbide ultrafine powder. The silicon carbide produced and prepared by the method is high in purity, the production efficiency is greatly improved, the production cost is reduced, products are consistent in density, uniform in composition and structure and good in reliability, and the silicon carbide ultrafine powder has a market prospect and is suitable for popularization.