The dislocation etch of the crystal grown by frustum platform and ordinary flat platform was observed by optical microscope. It was found that the dislocation distribution in the upper half of the crystal grown by the frustum platform was similar to that of the crystal grown by the flat platform, and its dislocation density in some areas was lower than that of the crystal grown on the flat platform. For the lower half of the crystal grown on the frustum platform, there were few dislocation defects on the prismatic faces, and the dislocations concentrated on the lower pyramidal surface that was in direct contact with the frustum. The existence of the lower pyramidal faces prevented the formation of new dislocations at the bottom of the prismatic faces and provided better growth conditions for the growth of the prismatic faces. Hardness analysis showed that the use of the frustum platform contributed to the crystalline perfection of the prismatic faces partly.