Abstract: In order to narrow the fluctuation of moisture content in output tobacco, a water supply system based on trend and deviation control was designed for the loosening and conditioning cylinder. The water supplying was changed from "front water supply" into "mainly front water supply compensated with rear water supply" to minimize the time lag between water supply point and detection point. An empirical data base of water supply coefficients for all cigarette brands was established to accurately determine the input water flow before and after conditioning and to implement prediction and feedback control of moisture content in output tobacco by combining trend control with deviation control. Cigarette brand "Taishan (Red General)" was tested in Jinan Cigarette Factory, and the results showed that the moisture content in output tobacco was automatically controlled, the standard deviation of the moisture content reduced by 0.29 percentage points, and the control stability was effectively improved. This technology provides a reference for reducing the time lag in tobacco processing control.