Objective: To study the regularity of extraction rate by comparing the extraction results between the compound and the individual traditional Chinese medicine, treating the solubility data by using Chrastil equation.Methods: SCCO 2 extraction, GC analysis, Chrastil equation.Results: The extraction rates of compound are clearly greater than the sum rates of individual angelica and ligusticum.Conclusion: The extraction rates of compound do not simply equal the sum of rates of individual angelica and ligusticum.