OBJECTIVE: To investigate the chemical constituents from the seeds of Cuscuta australis, from which about 90% commercial dodder was derived. METHODS:To isolate the flavonoides and sitosterol derivants, the solvent-extraction together with the column,chromatography and TLC methods were used. Several spectral methods such as IR,UV,¹H NMR,¹³C NMR and MS were used to determine the structure of the isolated constituents. RESULTS: In six constituents obtained,three were flavonoids,astragalin(Ⅰ)，kaempferol(Ⅴ)and quercetin(Ⅵ)，two were β-sitosterol(Ⅱ)and β-sitosterol-3-O-β-D-xylopyranoside(Ⅳ)，one novel compound,and the other one was lacceroic acid(Ⅲ).CONCLUSION:In this plant these compounds exceptβ-sitosterol have not been discovered previously.