Numerical study on gassolid flow field in the cyclone separator with different geometrical parameters was carried by using unsteady RSM model. The predictive models of the Euler number and cutoff size of cyclone separators based on response surface methodology was applied. The results showed that, the vortex finder diameter had a significant effect on the Euler number and cutoff size. With the increase of vortex finder diameter, the Euler number decreases rapidly and then increases slowly, the cutoff size increases. The effect of inlet height and inlet width on Euler number and cutoff size is ...