A novel class of (2E)-(2-oxo-1, 2-dihydro-3H-indol-3-ylidene)acetate derivatives were designed and synthesized as potent anti-proliferative agents. Most of these compounds showed potent anti-proliferative activity against some tumor cell lines, including SK-BR-3, MDA-MB-231, HCT-116, SW480, Ovcar-3, HL-60, Saos-2 and HepG2. Compounds 8c and 11h were identified as the most potent ones, while HL-60, HCT116 and MDA-MB-231 were the most sensitive cell lines. Mechanistic study revealed that compound 8c enhanced reactive oxygen species level by inhibiting TrxR and then induced apoptosis by activating apoptosis proteins, bax and cleaved-caspase 3 in HCT116 cells. Preliminary SAR analysis indicated that modifications of the double bond and ester group made great effects on the anti-proliferative activity. Our findings suggested that it was worth further studies on the antitumor potency of (2E)-(2-oxo-1, 2-dihydro-3H-indol-3-ylidene)acetates.