Objective: To take Buyanghuanwu Decoction as a model for exploring the variable rule of solubility parameters for the effective components group (fraction). Methods: To arrange the experiment design by uniform design and central composite plan, to determine the solubility parameter values with the modified inverse gas chromatography (IGC), and to fit the curve equation using SPSS software. Results: The recursive equation for the major active component including astragaloside (X1), ferulic acid (X2), paeoniflorin (X3), and ligustrazine (X4) was ...