The preparation process of ultrafine graphite powder is as follows: natural flake graphite and raw coke enter the crushing chamber by compressed air through feeding ejector, distribute in the nozzle outside the crushing chamber, and inject super-high-speed airflow into the crushing chamber, so that the coke powder collides and rubs with each other at high speed to form micro-powder, the air flow with micro-powder is discharged from the outlet tube into the classifying chamber, and the coarse particles are separated through the return tube. The remaining powder is collected by cyclone separator and bag collector. Ultrafine graphite powder was produced.