The objective of this paper is to propose a simple and effective pretreatment method for the enrichment of alkaloids.This pretreatment method was also applied to develop improved methods for the preparation of alkaloids from Scopolia tangutica Maxim.The chief member of this method was C 18 strong cation-exchanger for solid phase extraction (SPE).Besides hydrophobic interactions, cation exchange interactions can be used to improve the selection of this cartridge for alkaloids.The parameters used for our SPE method have been tested.The recoveries of isocorydine and nantenine were 92% and 95%, respectively.RSD values were 5.15% for isocorydine and 7.14% for nantenine.The maxima load mass were 14.5% and the SPE cartridge can be used more than 5 times.In the future, this SPE method has the potential to be utilized to enrich alkaloids from other plants enabling the preparation of alkaloids.