Cemented paste tailings(CPT) with high flowability and early strength was prepared with lead zinc tailings, Portland cement, and slag, using sodium sulfate as an alkali activator. Effects of sodium sulfate use level and slag to cement ratio on workability, compressive strength, setting time, phase composition, and microstructure of CPT were evaluated. The result shows that increasing the slag content in the mixtures leads to an increase in flowability, whereas the setting time is prolonged, and the early age strength is decreased. The use of sodium sulfate as an alkali activator shortens the setting time of CPT and promotes strength development, especially at the early age. Incorporating sodium sulfate provides SO2-4 that promotes the formation of ettringite, reduces the free water in the pore solution and leads to a densified structure. The use of sodium sulfate as an alkali activator raises the pH of the pore solution and accelerates the early age hydration of slag.