Objective:To establish a quantitative evaluation method for the color of Rhei Radix et Rhizoma charcoal in order to standardize the subjective and abstract sensory evaluation. Method:The red

green and blue values(RGB values) about the outer surface and powder color of Rhei Radix et Rhizoma and Rhei Radix et Rhizoma charcoal with different processing degree were determined

colors included already colored and uncolored.Correlation analysis was conducted by SPSS 19.0 statistical software. Result:Each color RGB values of each sample had the rule of R value>G value>B value

and the sum of RGB values was consistent with the corresponding values of R value

G value and B value.Through correlation analysis

there was a highly significant correlation between the color of the surface before and after colouring;and whether it's colored or not

there was a significant correlation between the outer surface color and the uncolored powder color

the correlation coefficients were 0.708 and 0.639. Conclusion:The sum of uncolored powder RGB values can objectively reflect the color information of Rhei Radix et Rhizoma charcoal.The method of quantitative analysis of the color of Rhei Radix et Rhizoma charcoal has been established to transform the abstract visual color into the quantified and figurative RGB values.The successful creation of this visual color makes the quantification and standardization of sensory evaluation possible

which will facilitate the improvement of the accuracy of traditional Chinese medicine(TCM) quality evaluation.At the same time

it also provides a certain experimental basis and reference for the quantitative and standardization of other TCM sensory evaluation.