Abstract: The invention discloses a single crystal growth method for a vertical high temperature and high pressure group III-V compound. A vertical high temperature and high pressure stove is capable of providing a group III element fusion zone with a temperature equal to or greater than that of a composition melting point and providing a group V element provision zone below the group III element fusion zone. The stove provides steam to the group III element fusion zone and the group V element provision zone at a temperature greater than evaporation temperature. The compound synthesis of a group III element and a group V element is completed in the group III element fusion zone, and an in-situ growth of single crystal is completed in the group III element fusion zone, thereby preventing the growth of the rich group III element and increasing the single crystal process efficiency.