The invention discloses a preparation method of ceramic powder. The preparation method comprises the following steps: delivering raw materials to obtain pre-mixture; smashing and slurrying the pre-mixture to obtain slurry; carrying out sieving and deironing on the slurry; carrying out spray granulation on the slurry subjected to the sieving and deironing. The step of smashing and slurrying the pre-mixture to obtain slurry is characterized in that the pre-mixture is smashed by a ball mill, the percent contents of ballstones of different diameters in the ball mill are 30mm to 40mm to 50mm to 60mm=(5 to 20) to (25 to 35) to (30 to 50) to (5 to 20), the revolving speed of the ball mill is 10-15 rpm, and the ballstones used by ball milling are high-aluminum ballstones. The preparation method is characterized in that the ballstones of different diameters are mutually cooperated to smash the pre-mixture, meanwhile, the slurry is subjected to deironing by a deironing slot and an electromagnetic de-ironing separator, the preparation efficiency of the ceramic powder is improved, energy consumption is small, and efficiency is high.