A new stilbene, (trans)-4-[2-(3, 5-dimethoxyphenyl) ethenyl]-1,2-benzenediol (1), was isolated from the whole herbs of Sphaerophysa salsula, together with (trans)-4-[2-(3, 5-dimethoxy phenyl) ethenyl]-2-methoxyphenol (2) and daucosterol. The structure of 1 was determined on the basis of spectroscopic evidences.