A new series of emodin derivatives was prepared and evaluated for their in vitro antiproliferative activity. Preliminary results revealed that these derivatives exhibited weak or negligible cytotoxicity at 10 lM against various cancer cell lines (i.e., K562, HepG2, and HCT116 cell lines) as well as normal hepatic cells (QSG7701). Interestingly, the evaluation for P-glycoprotein (P-gp) modulation indicated that they possessed potent P-gp inhibitory activity. Among them, the effect of compound 6 on P-gp inhibition was even greater than that of Verapamil, the known P-gp modulator. Therefore, the natural emodin scaffold could be employed as safe and effective modulator of P-gp mediated drug resistance in cancer chemotherapy.