The invention relates to a prefabricated member for a tertiary air hose elbow. The prefabricated member comprises a prefabricated brick body, wherein a connecting boss is arranged at the top end of the prefabricated brick body, a convex block is fixedly connected to the interior of the connecting boss, a groove is formed in the bottom end of the convex block, at least one screw rod is arranged at the bottom end of the convex block, and a plurality of flow deflectors are arranged on each outer side wall of the convex block. The prefabricated member has the advantages that because of the convex block arranged at the top end of the prefabricated brick body, in the airflow scouring process, the convex block is first scoured, flow distribution is performed through the flow deflectors arranged on the convex block, scouring to the prefabricated brick body caused after high-speed tertiary airflow turns can be effectively reduced, and therefore damage to the portion of the prefabricated brick body is greatly reduced, airflow is effectively distributed, the time in which the convex block is scoured by the airflow is shortened, the service life of the prefabricated brick is prolonged, after the convex block is abraded because of scouring, the angle of the convex block can be adjusted or the convex block can be correspondingly replaced according to the actual using condition, the work efficiency in maintenance is improved, and production cost is reduced.