Five known anthraquinones, physcion (1), I-O-methylemodin (2), emodin (3), physcion-8-O-β,-D-glucopyranoside (5), emodin-8-O-β,-D-glucopyranoside (6) and two known stilbenes, trans-resveratrol (4), trans-resveratrol-3-O-β,-D-glucopyranoside (7) were isolated from MeOH extract of Reynoutria sachalinensis (Polygonaceae). All structures were unambiguously established by 1D and 2D NMR and MS data and the compounds were evaluated for their cytotoxicity against L1210, HL-60, BI6F10 tumor cell lines in MTT assay. Among the compounds, trans-resveratrol (4) exhibited significant cytotoxic activity with IC50 values of 9.2, 6.7 and 9.8 μg/ml, against the test cell lines respectively, but compounds 1-3 exhibited the moderate cytotoxic activity.