The invention discloses a method for evaluating the quality of essence for tobaccos by using COD (chemistry oxygen demand) as an index. The method comprises the following steps: respectively determining chemistry oxygen demand (COD) values of a standard essence product and a sample to be determined, then, computing the relative deviation of the COD values of the sample to be determined and the standard product, and if the absolute value of the relative deviation is smaller than or equal to 10%, the sample is regarded as a qualified product, otherwise, the sample is regarded as the rejected product. The water is usually used as a solvent to determine the COD value, so that the relative content of organic compounds in an essence solution can be reflected to a certain degree; the relative deviation of the COD values of the sample to be determined and the standard product is computed to judge whether the content of the organic compounds in the essence meets the requirements or not. A quick clearing and spectroscopical spectrophotometry is combined. The method disclosed by the invention has the characteristics of being quick to identify, and being high in precision rate, and can be used as an index for effectively evaluating and controlling the quality of the essence for cigarettes.