Abstract: The methanol extract of Pteris wallichiana was separated and purified by MCI gel, sephadex LH 20, flash C18 and silica gel column chromatography combined with semi-pre HPLC. The chemical structures of the isolated compounds were identified by MS, IR, NMR, etc. Five sesquiterpene compounds were isolated from Pteris wallichiana and identified as 6,7-tetrahydrofuran-(2S, 3S)-pterosin C-3-O-β-D-(6′-acetyl)-Glu (1), (2S, 3S)-pterosin C-3-O-β-D-Glu (2), (2S)-pterosin A (3) and (2S)-13-hydroxyl-pterosin A (4), (2R, 3S)-2-hydroxyl-pterosin C (5). Compound 1 is a new sesquiterpene, compounds 3-5 were isolated for the first time. In vitro bioactivity assay showed that compound 1 was able to inhibit the proliferation of 4T1 and EMT6 cells, and possessed significant anti-triple-negative breast cancer bioactivity.