Abstract: Aconite alkaloids in two kinds of processed Radix Aconiti Kusnezoffii(RAK) were analyzed by ESI-MS. The results indicate that there are not diester-alkaloids detected in the two kinds of processed RAK by comparison with crude RAK, which show that both steaming process and boiling process decrease toxicity. As viewed from the loss of active components, steaming process is believed to be better than boiling process. At the same time, a simple, rapid and sensitive method is provided to analyze aconite alkaloids in different sorts of processed RAK using ESI-MS.