ObjectiveTo research and choose the best technology,conditions for estracting emod,in from Radix Polygoni Multiflori.MethodsAccording to physicochemical character of emodin from Radix Polygoni Multiflori,orthogonal design and tests of extract technology for emodin were carried out,and three factors were chosen such as quantity of ethyl alcohol,extracting time and the quantity of HCl,three levels of each factor were used for orthogonal design and test.ResultsThe optimal coditions were to extract refluently with 70% alcohol as much as ten times of the medicine amount for 0.5 and add 1%HCl as much as 15% of the solvent.ConclusionThe quantity of solvent and the puls quantity of HCl have a great influence upon the extracting efficiency of emodin.