The invention relates to a sintering method of alumina lump materials, and specifically relates to a method for sintering alumina powder into an alumina lump material used for sapphire crystal production through a flame fusion technique. The method comprises: sending the raw material of alumina powder to an alumina target ingot by a feeder, fusing the powder into an alumina sintered ingot througha combustor, then conducting pounding to make the ingot into an alumina lump material with a diameter of 5-40mm and density of 3.75-3.81g/cm<3>. The sintering process is directly carried out on a contactless high purity alumina target surface, and has no contact with other substances, thus being free of external contamination. The method of the invention solves the problems of low blank material density, easy pollution during production, low production efficiency and high production cost existing in current alumina lump material production, and satisfies the requirement of sapphire single crystals for high density lump materials.