The chemical constituents from the n-butanol fraction of Dendrobium huoshanense and their inhibitory effect on human gastric adenocarcinoma AGS cells were studied. The compounds from the n-butanol fraction of 90% ethanol extract of D. huoshanense were separated and purified by a series of chromatographic techniques,including silica gel column chromatography,D101 macroporous adsorption resin column chromatography,Sephadex LH-20 gel column chromatography. The structure of the compounds were identified with thin-layer chromatography,high-resolution mass spectrometry,and nuclear magnetic resonance spectroscopy methods. Eleven compounds from the n-butanol fraction of D. huoshanense were identified as α-D-arabinofuranoside (1), methyl β-D-fructofuranoside (2), α-D-glucopyranose (3), inositol (4), sucrose (5), 3-O-{[3′-O-β-D-glucopyranosyl-(1′′-3′)]-[6′-O-β-D-fructofuranosyl-(1′′′-6′)]-α-D-glucopyranosyl}-(+)-pinitol (6), β-D-glucopyranosyl-(2→1′)-2-O-β-L-arabinopyranosyl-(2′→1′′)-2′-O-β-L-arabinopyranosyl-(2′′→1′′′)-2′′-O-β-L-arabinopyranosyl-(2′′′→1′′′′)-2′′′-O-β-L-arabinopyranosyl-(2′′′′→1′′′′′)-2′′′′-O-β-L-arabinopyranoside (7), 5-hydroxymethylfurfural (8), syringic acid (9), chlorogenic acid (10), erianin (11). Compounds 1-3, 6, 7 were isolated from D. huoshanense for the first time. Compounds 1, 2, 6, and 7 were isolated from Dendrobium for the first time. The inhibitory effects of 11 compounds on the proliferation of AGS cells were evaluated using the MTT assay. For the first time, it was discovered that erianin (11) exhibited a significant inhibitory effect on the proliferation of AGS cells, with an IC₅₀ value (5.53 ± 1.20 µmol/L) significantly lower than that of the positive drug control (61.78 ± 3.57 µmol/L).