In order to investigate the movement and concentration distribution characteristics of catalyst particles in the riser outlet super vortex quick separation (SVQS) system, the gas-solid two-phase flow under different oil steam parameters was numerically simulated. Whereafter, particle size, concentration distribution and particles back mixing were analyzed. The simulation result showed that under a certain entrance concentration the particle concentration on the wall of the closing cylinder was greater with the greater density of oil steam or the smaller viscosity of oil steam, and distributed in a spiral strip with different bandwidth. A large number of particles gathered at the cover plate of the flow partition cylinder and formed a particle belt with periodic shedding characteristics. Moreover, the phenomenon of short circuit flow at the bottom of flow partition cylinder that weakened the separation performance of SVQS system. Particles with different sizes were always in a spiral layered arrangement when moving in a downspin, and the separation performance of SVQS system for fine particles with diameter below 0.013 mm was weak. With the increase of oil steam density or the decrease of viscosity, the particles following behavior became better, the particles concentration distribution was more uniform, and the SVQS system had a stronger ability to capture medium and fine particles. Particles back mixing also existed in SVQS system and decreased with the increase of oil steam density or the decrease of viscosity. Meanwhile, reducing particle back mixing and inhibiting particle concentration peak were important ways to improve the separation performance of the system.