Abstract: To accurately determine the residence time distribution of cut tobacco in a rotary cylinder,improve the processing quality of tobacco and provide a reference for the design and modification of rotary cylinders,a pulse tracing method was developed by taking CO₂ expanded cut tobacco as a tracer.The accuracy of this method was verified by the recovery of CO₂ expanded cut tobacco.Moreover,the effects of rotating speed of the cylinder and flow direction of medium on the residence time distribution were investigated.The results showed that:1) The developed method featured good repeatability,high accuracy and wide application range.2) With the increase of rotating speed of the cylinder,the average residence time of tobacco in cylinder reduced,while the dimensionless variance increased.3) The average residence time of tobacco in rotary cylinder was affected by the flow direction of medium;tobacco moved faster in a cocurrent cylinder than in a countercurrent cylinder.