Anaerobic fermentation of distiller's grains is an effective method to treat distiller's grains. The distiller's grains separation technology, based on a hydraulic pulper, simplifies the equipment and reduces energy consumption while ensuring the separation of rice husks and fermented organic matter. ANSYS Fluent, a widely used computational fluid dynamies (CDF) software, was used to simulate the two-phase flow of distiller's wastewater in the hydraulic pulper. The study focused on the mixed flow characteristics of rice husk, organic matter, and wastewater, investigating the velocity field, pressure field, composition field, flow line. as well as the steady state and transient flow fields, The simulation results showed that the slurry inside the curved blade at the top of the rotor reached a maximum velocity of 48.06 m/s and gradually decreased towards zero along the radial direction. Due to the rotor's high-speed rotation, a high-pressure zone and a low-pressure zone were formed on each side of the rotor, with a maximum working pressure of 3.06x10^5 Pa. The slurry exhibited centrifugal movement, with the pressure increasing radially from the center towards the wall. The flow around the center of the rotor formed a significant negative pressure, which drove the central slurry downward, and the pressure at the wall was the highest, reaching 0.125 MPa. The area below the rotor was considered a blind spot, with the fixed phase volume fraction reaching a maximum of 5.81%. Therefore, adjusting the rotor's height in the hydraulic pulper could be beneficial. During transient calculations, the desired mixingeffect could be achieved within an 8-min crushing process. Additionally, we summarized the mixed flow process of distiller's grains-wastewater: The distiller's grains from the top center started to fall under the action of gravity, and then were rotated by the rotor near the water pulper into the left or right vortex area, resulting in effective mixing with the slury. The distiller's grains from the top side quickly joined the swirling motion on the left and right sides as they descended because of gravity. The results are of importance for optimizing the operating parameters of distiller's grains-wastewater pulping.