Abstract: In order to rapidly determine the protein content in tobacco,the compositions of non-protein nitrogen was separated from water-soluble proteins by heating with acetic acid,and the content of non-protein nitrogen in tobacco was determined with continuous flow analyzer combining with UV catalytic device and online pressurized heater,then the content of protein in tobacco was calculated on the basis of measured non-protein nitrogen content.The results showed that:1) The detection results were stable with CV less than 3%;2) There was no significant difference between the detection results of this method and the current standard method,the result of T test was t=1.082,which was less than t_0.1,15=1.753;3) This method was reliable with the determining recoveries of non-protein nitrogen from 95% to 101%.