Abstract: The growth of flocs in flocculation process has a dynamic demand for hydraulic conditions. According to the theory of self-conservative coagulation kinetics, the design method of gradual change grid flocculation device is proposed, and a gradual change grid flocculation device is designed and processed with 300 S-1 as the initial velocity gradient. Under the optimized reagent condition, the experiments of flocculation and sedimentation of slime water in the designed device were carried out at the feed flowrate of 1.65, 2.28, 2.91 and 3.54 L/min. The results show that the floc size and the turbidity of supernatant are the best at 2.28 L / min, and the flow rate is close to the design value of 2.4 L/min, which shows that the design method is reasonable and reliable. Compared with the straight pipe flocculation and measuring cylinder turnover method flocculation sedimentation experiments, the turbidity of supernatant of slime water can be reduced by 12 NTU after flocculation sedimentation by gradual grid flocculation device, which indicates that the gradually reduced hydraulic velocity gradient in the device meets the requirements of flocculation kinetics and has advantages.