pH value is one of the most important factors affecting the treatment effect  of the additive agent combined vacuum preloading method on the construction waste slurry. Hence, the effects of pH on stability, flocculation and consolidation characteristics of construction waste slurry were studied. First of all, the changing law of the Zeta electric potential of soil particles in the waste slurry for different pH values was studied; then, the optimal amount of the flocculation agent of APAM added into the slurry with different pH values and the flocculation effects of the waste slurry prepared by different methods of adjusting pH values were studied; finally, the consolidation characteristics of the waste slurry with different pH values were analyzed based on the consolidation tests. The results show that: (1) the absolute value of Zeta electric potential on the surface of soil particles increases as the pH value of waste slurry decreases, and the particle size increases with the decrease of the pH value. Especially when the pH value is less than 7, the soil particles are easy to be aggregated and soil particles whose particle sizes are less than 0.01mm may turn to soil particles whose particle sizes are between 0.01mm and 0.02mm; (2) the particle size distribution curves are almost the same when the waste slurry reaches the best flocculation state, although the pH value of slurry is different. The optimal additive amount of APAM varies with the pH values; (3) the method of preparing the slurry with a certain pH value has a great influence on the flocculation effect on the waste slurry. The flocs of waste slurry prepared using CaO are larger in particle size compared to those prepared using NaOH; (4) the consolidation test results show that the consolidation coefficient of slurry reaches the peak value when pH value is close to be neutral. It is suggested that the pH value be adjusted to be neutral before the waste slurry is treated by the additive agent combined vacuum preloading method. The research results have practical significance for the treatment methods such as the additive agent combined vacuum preloading method, the filter pressing technique and the centrifugal method.