Aconiti lateralis Radix Praeparata is the lateral root of Aconitum carmichaeli Debeaux that belonging to Ranunculaceae family. It has been discovered that C 19 and C 20 diterpeneoid alkaloids are a kind of characteristic compounds from A. lateralis Radix Praeparata with complex structures and neurotoxic activities. The C 19 diterpenoid alkaloids are evolved from C 20 diterpenoid alkaloids, and they are the main effective components from A. lateralis Radix Praeparata. Moreover, C 19 and C 20 diterpeneoid alkaloids from A. lateralis Radix Praeparata have the characteristics of both efficacy and toxicity, and they are the main neurotoxic components from A. lateralis Radix Praeparata. Its toxicity mainly affects the central nervous system, and its toxic mechanism involves neurotransmitters, peroxides, ion channels, and so on. Overview of structure and neurotoxicity of C 19 and C 20 diterpeneoid alkaloids from A. lateralis Radix Praeparata is important for better developing the resources of A. lateralis Radix Praeparata and its clinical application.