The rising flow rate of the hydrolysis and acidification tank is the main parameter in designing the hydrolysis and acidification tank. The rising flow rate of the hydrolysis and acidification tank is related to the height and sludge concentration of the sludge layer in the tank. The water volume in the sewage treatment plant changes greatly in the morning and evening. The rising flow rate under the maximum flow rate, minimum flow rate and average flow rate should be selected for verification respectively. Under the maximum flow rate condition, Due to the expansion of the sludge layer, the sludge concentration decreases and the sedimentation speed of the sludge layer increases, which can automatically maintain the sludge concentration in the tank in a dynamic equilibrium state. At the minimum flow rate, the sludge concentration will increase, and the settling speed will decrease so that the sludge concentration can reach a dynamic balance. According to data from Beijing Miyun Sewage Treatment Plant, the sludge concentration is 20g/L under the highest flow condition, and can reach 60g/L under the lowest flow condition. The rising flow rate of the hydrolysis acidification tank sewage is 1.5-2.0m/h. The design scale of a city's sewage treatment plant in Heilongjiang is 20,000 t/d. The maximum upward flow rate of sewage in the hydrolysis and acidification tank is 1.76m/h, and the sludge concentration fluctuation range is 15-20g/L.