The invention relates to a large-specification silica loose body production method, which belongs to the technical field of quartz glass production. According to the invention, polyalkysiloxane raw material liquid is gasified and is subjected to a reaction with flame spitted by a combustor to generate the silica particles, through movement of the combustor, decrease and rotation of a deposition base rod, the silica particles are continuously laminated and decomposed on a base target surface; and the large-specification silica loose body is prepared. The method solves the problem that diameter of an ash material produced by a traditional production technology is small, production of large-specification quartz glass column (ingot) cannot be satisfied, deposition efficiency is low, uniformity of the loosening body material is poor, ventilating of the structure is insufficient, and gas phase processing or sintering for severe influence of the uniformity of the quartz glass column (ingot) at anaphase in the traditional production technology can be solved, and the method can provides the guarantee for subsequent production of large-specification quartz glass ingot with high uniformity.