Abstract: Objective :To investigate the inhibitory effect of Paeonol on the proliferation of human colorectal cancer cell line HT-29 and its synergetic effect with chemotherapy agents. Methods :The inhibitory effect of Paeonol, 5-FU, MMC, DDP with different concentration on human colorectal cancer cell line in vitro were detected by MTT assay, and the synergetic effect of Paeonol in low concentration with chemotherapy agents was observed. Results :Paeonol could inhibit the proliferation of HT -29 cells, which showed obvious concentration-effect and time-effect relationship. Pae in low concentration had synergetic effect in inhibiting the proliferation of HT-29 cells with several chemotherapy agents. Conclusions :Paeonol has a direct anti-cancer effect and can enhance the action of several chemotherapy agents markedly, which provides evidence to clinical application.