In order to reduce the environmental impact of waste slurry from the mixing station and promote the recycling of waste slurry, the influence of waste slurry on hydration and hardening process of cement was studied through the setting time, compressive strength, resistivity, hydration heat, pore structure test and hydration product analysis and by using waste slurry to replace part of mixing water. The results show that after adding waste slurry, the setting time of sample is shortened, the compressive strength increases, the second exothermic peak in the DSC curves appears in advance, 3 d resistivity increases, the amount of hydration products increases, and the porosity decreases. The higher waste slurry content is, the better the effect of coagulation is, and the higher hydration product Ca(OH)2 content is. When waste slurry content is 100% (mass fraction) and the storage time is 12 h, the initial setting time and the final setting time of sample are shortened by 69 and 87 min, respectively, compared with the blank group. At the age of 28 d, the production of Ca(OH)2 increases, and the improving effect of strength of sample is the best, which increases by 36.2% at 3 d, 32.7% at 7 d, and 8.1% at 28 d compared with the blank group.