A triterpenoid saponin was isolated from the pod of Gleditsia sinensis Lam.by ethanol extraction and silica gel column chromatography,and was identified by TLC,mp,IR,MS,₁H-NMR and ₁₃C-NMR.Its structure was determined to be 3-O-β-D-xylopyranosyl-（1→2)-α-L-arabinopyranosyl-（1→6)-β-D-glucopyranosyl oleanolic acid 28-O-β-D-xylopyranosyl-（1→3)-β-D-xylopyranosyl-（1→4)-α-L-rhamnopyranosyl-（1→2)-[（6S),（2E)-6-hydroxy-2,6-dimethy-2,7-octadienoyl-（1→3)and （6′S),（2′E)-6′-hydroxy-2′,6′-dimethy-2′,7′-octadienoyl-（1→6)]-β-D-glucopyranosyl ester.The acute toxicity experiment indicated that the tolerance dose to mouse was 160～400 mg/kg through mouth,and LD₅₀ was 249.52 mg/kg,with the 95% confidence limit of 224.81～276.95 mg/kg.Its toxicity to mice is greater than that of gleditsioside A.The research results show that the gleditsioside O is the main active ingredient in rat-killing.