Abstract: In order to reduce the amount of tobacco built up on the inside wall of conditioning cylinder and the fluctuation of moisture content in expanded tobacco, the conditioning system was improved with the three-step humidifying technology. A humidifying hopper and a humidifying vibrating trough were added to complete the wetting process together with the conditioning cylinder and improve the processing characteristics of tobacco step by step. The nozzle system and lifting paddles in the conditioning cylinder were modified to adapt to lower intensity of water supplying. The improved conditioning system was tested with expanded tobacco of Grade A provided by Xiamen Tobacco Industrial Limited Corporation, and the results showed that the filling value, yield and integral strand proportion of expanded tobacco increased by 0.82 cm³/g, 1.28 percentage points and 1.88 percentage points respectively; the short strand proportion, the amount of tobacco buildup on cylinder wall and the standard deviation of moisture content decreased by 1.22 percentage points, 12.39 kg/batch, 0.039 percentage points respectively. This technology provides a support for promoting the quality of expanded tobacco.