Abstract: The tobacco sample was extracted with 0.5% acetic acid boiled for fifteen minutes, filtrated, and washed with 0.5% acetic acid, during which the water soluble nitrogen was removed.Then, the sample residue was(digested) in the presence of 0.1g HgO, 1.0g K-2SO-4 and 5mL concentrated sulphuric acid.The protein in resultant digestion solution was determined with an autoanalyzer.The results showed that the relative standard deviation of the method was 1.1%, and the recoveries were from 98% to 102%.The protein in some tobacco leaves were also(determined).