To investigate the chemical constituents of the Rheum Tataricum and evaluate some of the compounds for cytotoxic activity against Hela cell.Methods:Silica gel，Sephadex LH-20 column，chromatography High Performance Liquid Chromatography methods were used to do isolation.The structures of isolates were confirmed by spectral (LC/MS，1H-NMR，13C-NMR，2DNMR，thin-layer chromatograph) analysis and by comparison with the literature reports; Cytotoxic activities were determined by the SRB method.Results:Eleven compounds were gained and they were chrysophanol (1)，emodin(2)，Physcion (3)，Aloe-emodin (4)，Rheosmin (5)，1，3，8-trihydroxyanthraquinone (6)， Sitosterol (7)， Daucosterol (8)，emodin8-O-β(6-O-acety)glucopyranoside （9），physcion1-O-β(6-O-acety)glucopyranoside （10），chrysophanol1-O-β(6-O-acety)glucopyranoside （11）; six compounds were evaluated for cytotoxic activities，five of them showed cytotoxic activity against Hela cell，and they were Aloe-emodin，1，3，8-trihydroxyanthraquinone，emodin8-O-β(6-O-acety)glucopyranoside，physcion1-O-β(6-O-acety)glucopyranoside，chrysophanol1-O-β(6-O-acety)glucopyranoside，rheosmin has no activity.Conclusion:Eight (compound 4-11)of them are isolated from Rheum nobile for the first time; five of the compounds show cytotoxic activities，compound5，6，9，10，11are evaluated for cytotoxic activities against Hela cell for the first time.