Smilax glabra is a well-known traditional Chinese medicine which has been used clinically to prevent leptospirosis, to treat syphilis, and acute bacterial dysentery, etc. Its extracts showed anti-tumor and anti-atherosclerosis activity. A new isoflavone, 7,6'-dihydroxy 3'-methoxy isoflavone (1), along with two known compounds taxifolin (2) and astilbin (3), have been isolated from the roots of Smilax glabra. The structures were elucidated by spectroscopic methods including 2DNMR techniques.