Abstract: In order to investigate the periodic pulsation caused by vortex core of cyclone separators, Reynolds stress model (RSM) was used to simulate the 3D unsteady flow field of two-stage cyclone separators, and the pulsation characteristics of the first and second separators were analyzed. The results show that the main frequency of first separator is consistent with the second, but there are double and triple frequencies in the second separator. The radius of vortex core decreased with the decrease of axial height and the frequency and amplitude increased with the increase of inlet velocity. The results showed good agreement with on-site data and are helpful for the improvement of two-stage cyclone separators.