Abstract: Using RNG k−ε turbulence model, VOF multiphase flow model and Eulerian Multi−fluid VOF model, the flow field and particle motion behavior in spirals were numerically simulated. The evolution characteristics of water flow field parameters, hematite−quartz slurry flow field parameters, particle distribution and separation efficiency with the turn number of fluid flows through the trough under conditions of smooth wall as well as rough wall were systematically investigated. It was shown that in comparison to the water system, local bulges were observed in the slurry flow film, accompanied by an increase in the tangential velocity of the slurry fluid in the inner edge region and a decrease in the tangential velocity at the middle and outer edges. The radial velocity distribution exhibited noticeable fluctuation characteristics. Compared to the condition of smooth wall, that of rough wall resulted in a reduction of bulges height of the slurry flow film. Additionally, the tangential velocity of the slurry was generally higher, and the difference in tangential velocity at the inner edge of the slurry was smaller. The intensity of the internal circulation weakened while the intensity of the external circulation strengthened. When the longitudinal path of the fluid reached the third turn, the radial distribution difference of flow field parameters were reduced and became similar. Compared with the condition of smooth wall, the distribution of hematite particles decreased in the inner half trough under the condition of rough wall , and the inward migration amount increased with the turn number of fluid flows through the trough, but the amount of stay in the outermost micro−region of the outer edge also increased. Quartz particles formed more distribution in the middle area of the trough of the third turn gradually with the flow field evolution. The maximum separation efficiency of hematite and quartz increased with the turn number of fluid flows through the trough and achieved balance gradually. The maximum separation efficiency of hematite and quartz decreased under the condition of rough wall. It is found that rough wall affected the slurry flow field and particles separation behavior of spirals significantly within the scope of this research, which could provide a reference for the wall roughness design and process control of spirals.