CFD simulation has become an effective way to study the mixing and segregation characteristics of gas-solid flow in CFB risers, which is important for the proper operation and design of such reactors. In this study, the numerical solution of a recently developed EMMS drag model for binary gas-solid flow which considers the effect of particle clustering structures on the interphase drag forces was first improved, it was then coupled with a multifluid model to perform extensive 3D simulations of the mixing and segregation pattern of binary gas-solid flow in CFB risers. It was shown that the experimental data of axial solid concentration profiles and radial solid mass flux distributions can be captured reasonably by the combined EMMS-multifluid model, indicating that the model is able to reproduce the hydrodynamics of complex gas-solid flow with particle size distribution.