The invention discloses a prefabricated member for a lime rotary kiln adopting magnesium-rich magnesium-aluminum spinel waste bricks as main raw materials and a preparation method of the prefabricated member. The invention adopts a technical scheme as follows: the prefabricated member is prepared from the following components in percentage by weight: 35 to 40 percent of 1 to 3 mm magnesium-rich magnesium-aluminum spinel waste bricks, 18 to 25 percent of 0.088 to 1 mm magnesium-rich magnesium-aluminum spinel waste bricks, 30 to 35 percent of magnesium-rich magnesium-aluminum spinel waste bricks less than or equal to 0.088 mm, 3 to 6 percent of silicon nitride fine powder less than or equal to 0.03 mm, 0.05 to 1 percent of metal aluminum powder less than or equal to 0.246 mm, and 4 to 6 percent of composite binding agent; and the added water accounts for 5 to 6 percent of the total weight of the main raw materials; the composite binding agent is prepared from 20 to 40 weight percent of silica powder and 60 to 80 weight percent of aluminate cement, wherein the weight percentage content of SiO2 in the silica powder is more than or equal to 93 percent, and the weight percentage content of Al2O3 in the aluminate cement is more than or equal to 68.75 percent. The preparation method comprises the steps of crushing, screening, grinding, burdening, forming, drying, heat treatment and the like. The prefabricated member adopts the waste bricks as the main raw materials, so that the price is low; and by introducing silicon nitride, the metal aluminum powder and the composite binding agent, the performance and the quality of the prefabricated member can be remarkably improved.