To optimize the extraction process for radix scrophulariae by central composite design and response surface methodology.Methods:Central composite design and response surface methodology was used to optimize the extracting process.The main influential factors of extraction efficiency are ethanol concentration，solvent ratio and reflux time.The conditions of the extraction were evaluated by the total content of harpagide and harpagoside.Results:Analysis indicated the optimum conditions of harpagide and harpagoside are 18%~32% ethanol，20~26 fold solvent，ultrasonic extraction 30~48 minutes.Conclusion:It shows that the optimum process for extracting radix scrophulariae is simple，more convenient and with higher precision.