Making alkaline ionic liquid ［Mmim］ DMP and using it as solvent by microwave heating，the effective removal of lignin in tobacco stems of reconstituted tobacco was studied. A rapid and accurate method for quantitative determination of liquid lignin by using UV spectrometry was established. The optimum technology for the removal of lignin in tobacco stems with the ionic liquids was determined by orthogonal experiment as follows: a maceration temperature of 80℃，a maceration time of 25 min and a solid /liquid ratio of 1∶15. In this process，the removal rate of lignin was 22.60%. The removal rate was about 5 times of that of water extraction. After extraction of tobacco stems by using ionic liquids，the fillers of fiber were removed heavily and the fiber profile was clearer，which were conducive to the pulping of the subsequent raw materials and the control of smoke quality.