The invention provides a water-soluble monodemethoxycurcumin derivative as shown in general formula I and a pharmaceutically acceptable salt thereof. The compound has higher water solubility as well as high antitumor activity, has a function of inhibiting human gastric carcinoma cells MGC-803, human hepatocellular carcinoma cells Bel-7402, human chronic leukemia granulocytes K562 and human glioma U87 to different extents, and can be used for preparing an antitumor medicament, and the IC50 (Inhibitory Concentration 50) reaches the level of 1 [mu]M.