Abstract: A new rapid, quality control method based on quantitative water tests has been established for the quality evaluation of Indigo Naturalis. The Turbiscan stability index (TSI) of 26 batches of Indigo Naturalis was measured by a stability analyzer. The parameters, including the method by which the ingredients are added, their particle size, amount, and the testing temperature, were systematically optimized and the methodological indexes such as repeatability and stability were determined. The content of indigo and indirubin in 26 batches of Indigo Naturalis was determined by high performance liquid chromatography and the total ash was measured. The correlation analysis between the active ingredients, total ash content and TSI value of Indigo Naturalis was determined by SPSS 26.0 and Origin 2021. This research shows that the best way to prepare samples for testing is to add 0.2 g of Indigo Naturalis powder which has passed through a No. 7 sieve but failed to pass through a No. 9 sieve to a glass bottle containing 20 mL pure water by a funnel and scan at 25 ℃ with a stability analyzer. Consistency analysis showed that the content ranking of indigo and indirubin is opposite to the TSI value, and the content ranking of total ash is generally consistent with the TSI value. Correlation analysis showed that the correlation coefficients of indigo and indirubin content and TSI value were -0.850 and -0.801, respectively, and R² was 0.72 and 0.64. The correlation coefficient between total ash content and TSI value was 0.724, R² was 0.52. Using the change in TSI value of Indigo Naturalis powder in water, this study establishes the range of classification of Indigo Naturalis decoction pieces and the content of relevant components, which can be used to authenticate Indigo Naturalis and evaluate its quality.