Abstract: A bioactive compound was obtained from the ethanol extract of the Dodonaea viscosa (Linn.) Jacq. Enum. seeds using separation technologies including pore resin, gel SephadexLH-20, reversed phase chromatography ODS and preparative high performance liquid chromatography (Pre-HPLC). The structures of compound 1 were characterized by NMR experiments and mass spectrometry as a new oleanane-type triterpenoid, 21-epoxyangeloyl-15,16,28-tirhydroxy-22-(2-meth-ylbutanoyl)-Olean-12-en-3-(O-α-L-arabinofuranosyl-(1→3)-O-β-D-glucopyranosyl-(1→2)-β-D-glucuronide. It was named as dodoneaviscoside A. The results of the bioactivity determination showed that dodoneaviscoside A had antifeedant activity against the 3^th instar larvae of Plutella xylostella (L.) with AFC₅₀ value of 207.4 μg/mL. As a new compound with good nonselective antifeeding activity to P. xylostella, the potential applicatio of dodoneaviscoside A is worth of further investigation.