Abstract: Taking copper tailings as an experimental object, dynamic thickening experiments were conducted by adding 0, 10, 25, 40 and 55 g of anionic polyacrylamide (APAM) pei tonne of the tailings, respectively. It was found that the thickening concentration of the tailings at the prophase (1 h) increased gradually from 63.98% to 68.20% with increasing flocculant dosage, but at the anaphase (12 h) the value fell slightly when the flocculant dosage increased. In combination with experimental results, the flocculant dosage was divided into four intervals from less to more, low concentration (0 to 10 g per tonne of the railings), appropriate concentration (10 to 25 g per tonne of the tailings), high concentration (25 to 40 g per tonne of the tailings), and ultrahigh concentration (40 to 55 g per tonne of the tailings). The influence mechanisms of fiocculant dosage on railings thickening in the different intervals were put forward, which present partial adsorption, adsorption bridging, protection, and encapsulation roles, respectively.