The invention relates to a red long-afterglow luminescent material and a preparation method thereof. The chemical expression of the red long-afterglow luminescent material is (Ca1-x-y-a-b-delta SrxBay)2Nb2O7:Pra, Rb, wherein x is more than or equal to 0 and less than or equal to 0.2, y is more than or equal to 0 and less than or equal to 0.1, a is less than or equal to 0.03 and more than 0, b is more than or equal to 0 and less than or equal to 0.03, delta is more than or equal to 0 and less than or equal to 0.1, and R expresses a rare earth element and selected from one or more of La, Nd, Sm, Eu, Gd, Yb and Lu. The red long-afterglow luminescent material is synthesized in the air by adopting a high-temperature solid phase method, the red long-afterglow luminescent material has obvious red long-afterglow characteristic after being activated by ultraviolet light or sunlight, an emission peak is positioned on a 614-nanometer position, and the longest afterglow observable time exceeds 30 minutes in a dark place under naked eyes. The preparation method disclosed by the invention is simple and easy to operate and can be used for large-scale production without a reducing atmosphere. The red long-afterglow luminescent material disclosed by the invention has the advantages of stability in physicochemical property, high brightness, good monochromaticity and long afterglow time and belongs to an environment-friendly material; according to the red long-afterglow luminescent material, the matrix elements, namely Ca, Sr, Ba, Nb and O, are all tellurian rich elements, and only a small quantity of rare earth elements are adopted, so that no physical injury and environmental pollution are generated in the production and usage of the material.