To study the influence of admixtures, including blast furnace slag, quicklime, and fly ash, on the properties of solidified uranium mill tailings, the mechanical strength, permeability coefficient, and radon exhalation rate of solidified samples were measured after curing and storage for 28 days. The results showed that, with increased admixture dosage, the curing degree of the solidified body improved, mechanical strength increased, and permeability coefficient and radon exhalation rate decreased. At the same dosage of the three additives, the optimized curing degree in the blast furnace slag samples with 25% dosage had the properties of blast furnace slag samples, which was in accordance with China GB 14569.1-2011 standards that provide theoretical reference and decision evidence for the future management of uranium tailing impoundment/decommissioning treatment.