Abstract: Swirl flow field of a pneumatic conveying system is investigated experimentally.The swirling flow is imparted to the flow by the use of swirl vanes.A five hole probe is used for measuring the tangential angle of flow、axial velocity、static pressure of flow and swirl number in the flow sections of the conveying system.It is shown that the existence of central screw conveyer produces the contrary swirl flow under some of the swirl vane angle condition.The larger axial velocity is produced in the outer annular layer of flow.The maximum value of swirl number in the flow sections is agreed with the simplified theoretical relation.