Activity-guided fractionation of Neosinocalamus affinis leaves led to obtain two new flavonoids, 4 '-O-((7 '' R,8 '' S)-8 ''-guaiacylglyceryl)-pleioside B (9) and apigenin 6-C-beta-d-fucopyranosyl-7-O-beta-d-glucopyranoside (10) along with eight known compounds. Their structures were elucidated on the basis of spectroscopic data (UV, IR, NMR, and MS). Among these 10 compounds, farobin A (4) and isoorientin (7) showed significant antioxidant activity evaluated by 1,1-diphenyl-2-picrylhydrazyl, 2,2 '-azinobis(3-ethylbenzothiazoline-6-sulfonic acid), superoxide anion and nitric oxide (NO) radical-scavenging assays.