This paper reviews the research progress on antitumor mechanism of curcumin. Curcumin shows a certain efficacy on many kinds of cancer, such as colon, breast and pancreas cancer. At present, many molecular biological mechanisms are considered to be associated with the antitumor effects of curcumin,including regulating the unlimited proliferation of cancer cells and inducing apoptosis, regulating various signal pathways, inhibiting tumor angiogenesis and inhibiting metastasis.