Abstract: To address the deterioration of paste rheological performance caused by increasing fine tailings in deep mining, the mechanism of the effect of fine particle (diameter ＜ 20 μm) content on slurry rheological properties was investigated, and the multi-dimensional regulation effects were evaluated. The results show that a critical threshold of 30% exists for the fine particle content. When fine particle content ≤ 30%, physical filling dominates, with the initial slurry porosity decreasing from 28.5% to 21.8% and the static yield stress increasing gently from 4.2 Pa to 45.8 Pa. When fine particle content ＞30%, the interparticle spacing shortens to below 10 nm, shifting the dominant mechanism to electrochemical flocculation induced by van der Waals attraction. The effective free water content drops sharply from 1.05 g to 0.42 g, triggering a non-linear, exponential growth of static yield stress, which reaches 1 250.0 Pa at fine particle content = 50%. By employing a synergistic strategy of "grading reconstruction-critical concentration-electrical regulation," the initial porosity was reduced from 38.5% to 12.1%. Combined with a chemical water-reducing agent to increase the absolute value of Zeta potential to 32.1 mV, the static yield stress was reduced by up to 98.1%, converting the slurry into a stable shear-thinning state. This study provides a design basis for the low-resistance, long-distance transportation of high-concentration paste.