The invention discloses a manganese ion-activated red long-afterglow luminescent material and a preparation method thereof, and belongs to the technical field of long-afterglow luminescent materials. The long-afterglow luminescent material comprises two components, namely AlN:Mn<2+>, wherein AlN is a matrix, and Mn<2+> is an activation ion. The preparation method of the material comprises the following steps of: based on aluminum nitride and manganese carbonate as raw materials, fully mixing the raw materials and placing into a boron nitride crucible; covering the boron nitride crucible; firing under the nitrogen atmosphere; and cooling to prepare the manganese ion-activated red long-afterglow luminescent material. The preparation method is simple to operate; and the prepared long-afterglow luminescent material is good in performance, and the afterglow time can continuously last for more than 2 hours in the dark environment. The long-afterglow luminescent material is low in production cost, stable in chemical property of the product, fluffy and easy to grind, and is free of radioactivity; and therefore, the harm to the environment can be avoided.