In an attempt to develop potent and selective anti-tumor agents, two novel series of artemisinin-chalcone hybrids were designed, synthesized and screened for their antitumor activities against HT-29, A549, MDA-MB-231, HeLa and H460 cell lines in vitro. Nearly all of the tested compounds showed significantly increased anti-tumor activity compared with the corresponding dihydroartemisinin (DHA). Most of the title compounds displayed good selectivity toward HT-29 and HeLa cell lines with IC50 values ranging from 0.09 to 0.85 μM. Among them, the most promising compound 9c (IC50 range of 0.09—0.93 μM) was 10.5- to 70-times more active than DHA (IC50 range of 5.6—15.6 μM) respectively.