Abstract: The hydrolyzation process of aconitum diterpenoid alkaloids was studied, and the reaction type was defined according to its optimized experimental conditions. Electrospray ionization mass spectrometry (ESI-MS) was introduced to compare the difference in alkaloids types among the extraction of crude aconite roots and prepared aconite roots. After processing of crude aconite roots, most of the diester diterpenoid alkaloids converted to the monoester form, while C₈ was the major location for such reaction. It is a typical alkali-catalyzed hydrolysis derived from the decomposition of the alkoxy chain.