The invention relates to a method for processing the content of alkali in alumina red mud. The method comprises the following steps of: 1, pulping the alumina red mud, and feeding slurry into a dealkalization reaction tank; 2, dealkalizing: adding a dealkalizing agent into the red mud slurry, uniformly stirring, rapidly reacting the dealkalizing agent in the reaction tank, and carrying out solid-liquid separation after reacting; 3, roasting and reducing: reducing the dealkalized red mud by adopting an iron oxide roasting and reducing process; and 4, magnetically separating: feeding the red mud into a magnetic separator by using a mortar pump so that the red mud is separated into magnetic red mud and non-magnetic red mud, feeding the magnetic red mud into a ball mill to be ball-milled, after filter-pressing and drying the non-magnetic red mud, taking the non-magnetic red mud separated through magnetic separation for two times as medium and fine sands for dry mortar, for later use, and exciting and activating components of SiO2 and AL2O3 in the red mud by adding alkaline materials, such as carbide slag or limestone powder and the like. The method disclosed by the invention has the characteristics of simple process and low investment, so that the alkali content in the red mud is greatly reduced.