Abstract: A spectrophotometric method is presented for the determination of ammonia in tobacco. Determination of ammonia based on the reaction with Chloramine-T and Thymol to give a color compound in an alkaline solution. The maxium absorbance of the compound is at 670nm, and Beer's law is obeyed in the range of 0~6μg/ml.Ammonia in tobacco were determined by the proposed method, and its recovery rate is 96%~100%, relative standard deviation is less than 0.30%.