In order to investigate the residence time distribution of cut tobacco in rotary cylinders and improve the quality of processed tobacco,a method for determining the residence time distribution of cut tobacco in a rotary cylinder was developed with a negative step trace method by taking CO2 expanded cut tobacco as a tracer,and the effects of rotation speed of cylinder and material throughput on the residence time distribution were analyzed.The results showed that:1) the developed method featured less test time and good repeatability;2) with the increase of cylinder rotation speed and material throughput,the average and minimum residence time decreased,while dimensionless variance increased.