Abstract: In order to avoid the occurrence of wet tobacco caking after expanded tobacco leaving the conditioning cylinder, the water addition and tobacco movement inside the conditioning cylinder were simulated with Fluent simulation software following analysis of the working principle of the conditioning cylinder. On the basis of simulation results, the nozzles' arrangement inside the conditioning cylinder were optimized, and the amount and rate of water addition were adjusted as well. The modified conditioning cylinder was tested on the tobacco expansion system in Ningbo Cigarette Factory, the results showed that all the technical indexes of the processed expanded tobacco met production requirements without compromise of tobacco quality; the caking rate decreased from 11.75‱ to 0.37‱, or reduced by 96.9%; which effectively promoted the conditioning effect of expanded tobacco. This technology provides a technical support for improving expanded tobacco processing technology.