Preparation method of silicon carbide single crystal

The invention relates to the field of silicon carbide single crystals and discloses a preparation method of the silicon carbide single crystal. The preparation method comprises the following steps: putting a crucible filled with a silicon carbide raw material into an autochave, heating the silicon carbide raw material for sublimating, recrystallizing the sublimated material on a seed crystal and cooling the crystal to obtain the silicon carbide single crystal. A heating mode is realized by the sequentially-performed stages: firstly, maintaining for 10 to 20 minutes under the conditions that the temperature is 1200 to 1300DEG C and the pressure is 550 to 650 torr; secondly, keeping the pressure at 550 to 650 torr and raising the temperature to be 2100 to 2200DEG C; thirdly, reducing the pressure to be 350 to 450 torr and maintaining for 20 to 40 minutes; fourthly, reducing the pressure to be 1 to 2 torr, and maintaining for 30 to 40 hours; fifthly, raising the pressure to be 350 to 450 torr, and maintaining for 20 to 40 minutes; sixthly, raising the pressure to be 550 to 650 torr. According to the method, the silicon carbide single crystal with large size and high quality can be obtained.