The invention relates to a geopolymer taking stone coal vanadium extracted tailings as major raw materials and a preparation method thereof. According to the technical scheme, the geopolymer is prepared from the following components in percentage by weight: 57-78 percent of stone coal vanadium extracted tailings, 5.5-10 percent of silicon-aluminum corrective addition, 10-18 percent of solid base excitant, 1-3.5 percent of water-proofing agent, 2-10 percent of stuffing and 2-10 percent of deionized water. The preparation method comprises the following steps of: adding a base excitant solution prepared by dissolving the solid base excitant in the deionized water into a mixture prepared from the stone coal vanadium extracted tailings and the silicon-aluminum corrective addition, and stirring; adding the water-proofing agent and stuffing, and stirring; and performing press forming, coating a molded blank with a plastic film, curing, demolding and standing at room temperature. The preparation method has a simple process, low cost and low energy consumption; and the geopolymer has high compression strength, high dry-shrinkage resistance and high impermeability, and is prevented from scumming after standing for a long time.