The current status of the development of the particle collection theory for cyclone separators, including the theories of equilibrium-orbit, time-of-flight, hybrid and CFD (Computational Fluid Dynamics), is summarized in this paper. In order to evaluate their predictive availability, several gas-particle separation models representing the different approaches for calculation of the collection in a cyclone, are compared with the grade efficiency curves generated from experimental measurements. The results show that both the Mothes and Loffler and Iozia and Leith theories can perform better in the semi-empirical theory, and also demonstrate that the CFD theory is a more fundamental and basic method, which is capable of modeling the particle collection in cyclone separators.