Segregation exists extensively in the circulating fluidized bed (CFB) system, with solid particles of different sizes and densities. This paper studied the segregation of binary particles in a CFB system. Experimental results showed that segregation in the riser became weaker with increasing fluidizing gas velocity, u(g), and solid circulating rate, G(s). In the case of high u(g) (6.0 m/s) and high G(s), segregation almost disappeared and the binary particles in the whole system became complete mixing. The average jetsam mass fraction along the riser height showed different relations with the initial jetsam mass fraction in the literature. In order to explain the discrepancy in the literature, this paper indicated the exit geometry influenced the segregation in the whole CFB loop, i.e. not only in the riser, but also in the external loop. For the abrupt exit, the internal refluxing of solids always existed in the sharp bend for the inertial separation of particles, and more coarse particles rebounded at the riser exit than the fine particles. Thus more coarse particles stayed in the riser than in the standpipe. (C) 2018 Elsevier B.V. All rights reserved.