Abstract: In order to probe into the separation mechanism of the FXX cyclone dust collector for providing a theoretical guidance for optimizing its process parameters and hence working performance, an analysis is made of the tangential, radial and axial velocity distribution patterns of the FXX 18cyclone dust collector′s internal flow field, through numerical simulation using the FLUENT module of ANSYS software and the K-epsilon model in viscous model. Result of analysis shows that its internal flow field exhibits more or less an axial symmetry, and the pressure loss tends to increase sharply with the increase of inlet velocity.