Abstract: With the continuous pursuit of mineral resources and the development of mineral processing technology, ore is being ground more and more finely, which has resulted in large volumes of ultrafine tailings. However, ultrafine tailings are more difficult to separate from water than coarse tailings, which also makes the safe and efficient disposal of these tailings difficult. Normally, flocculation is an essential part of solid-liquid separation to improve the settling rate, and a polymer flocculant is widely used in treating ultrafine tailings. To study the influence of flocculation conditions on the flocculation effect, ultra-flocculation theory and the UltraflocTester UFT-TFS-029 were used. The relative flocculation rate was applied to characterize the flocculation behavior of artificial ultrafine tailings under the conditions of pH 9-12, flocculant dosage f_d=2 g·t^-1-20 g·t^-1, shear rate γ=100 s^-1-2000 s^-1, and solid volume fraction φ=2%-14%. The results indicate that the flocculation rate increases first and then decreases with pH, flocculant dosage, and shear rate. However, this rate decreases gradually with an increase in the solid volume fraction. The optimal flocculation conditions are: pH 11, f_d=12 g·t^-1, γ=500 s^-1, and φ=4%. Also, to achieve the optimal flocculation rate, the dependence of the optimal shear rate on the solid volume fraction also increases with the solid volume fraction. Therefore, it is necessary to adjust the operating parameters such as pH, flocculant dosage, shear rate, and solid volume fraction to achieve optimal flocculation. A satisfactory flocculation rate of ultrafine tailings is easily achieved in a very short time using the ultra-flocculation theory, which provides a reference for the design of feed wells based on shear rate and residence time.