Abstract: FCC slurry oil, rich in polycyclic aromatic hydrocarbons, is an ideal raw material of high value-added petroleum products such as carbon fiber, needle coke and carbon black. However, their uses are limited by the interior solid particles. The removal of solid particles in slurry oil is essential to improve its applicability. The viscosity of the slurry, density difference between the slurry and particle, and particle size are the key factors to influence the sedimentation of solid particles in slurry oil. Here, the effect of the addition of petroleum ether and sedimentation temperature were tested to optimize the viscosity of the slurry and density difference. The McLaughlin method was applied to calculate the settlement velocity in the slurry oil in the settlement experiments. The characteristics change of slurry oil and the sedimentation laws of particles of different sizes were analyzed to obtain a settlement velocity model. The results showed that the error between experiment and model method was within 10%. It was also suggested that the sedimentation temperature and the loading amount of petroleum ether significantly affected the viscosity of the slurry oil as well as the settlement behavior. As the viscosity decreased, the particle settling speed increased. In addition, the sedimentation laws of particles of different sizes were dramatically different. The sedimentation rate of the particles with a diameter larger than 40 μm was significantly influenced by the process conditions, while that for smaller particles with a diameter below 20 μm was relatively less influenced. This study offers an insight into improving the separation efficiency of solid particles during FCC slurry settlement process.