Cyclone separators play a dominating role in fluid catalytic cracking, biomass pyrolysis, dedusting, demisting, heavy oil regrading, etc. Separation mechanism, pressure drop, particle size, collection efficiency, gas underflow, gas inlet velocity, particle loading, cut‐off size of particles, and gas residence time are the main cyclone performance criteria. In the present work, the particle separation theory is explained and recent developments of numerical simulations of different cyclone separators with tangential inlet are summarized. Besides, the effect of different parameters on cyclone performance is discussed and several suggestions are provided based on previous numerical simulations.