When the tailings still do not reach the expected concentration under the traditional dewatering process conditions, the addition of admixture is an effective means to achieve secondary rapid dewatering. For the problem that the copper ore tailings are fine and the bleeding ability is poor, and the concentration is still not up to standard after dewatering by the deep cone thickener, the secondary dewatering experiment is carried out by adding the A-type admixture and the B-type admixture, and the admixture is not added as the control. The experimental results showed that the bleeding amount of slurry with admixture was significantly greater than that without admixture for 1h and 2h. With the increase of bleeding time, the bleeding amount of slurry with admixture and without admixture was basically equal at 4h. Through the regression equation of dewatering mass fraction and dewatering time in three cases, the mathematical model of secondary dewatering of concentrated tailings was obtained, the relationship between the secondary dewatering mass fraction and the dewatering time is exponential function. Finally, the mechanism of rapid dewatering and structural strengthening of tailings by admixture was analyzed. The admixture not only increased the dewatering concentration of tailings, but also increased the stability of tailings, which has potential engineering application value.