Series of novel derivatives of 6-chloro-quinazolin, which this moiety was linked to a 1,5-diaryl-1,4-pentadien-3-one system, have been synthesized and tested for their antitumor activities in vitro against a panel of three human cancer cell lines (MGC-803, Bcap-37, and PC3 cells). Bioassay results indicated that most of the prepared compounds demonstrated good activities against various cancer cells. 6-chloro-quinazolin derivatives 5a and 5f were the most active members in this study, and experimental results of fluorescent staining and flow cytometry analysis revealed that they could induce apoptosis in MGC-803 and Bcap-37 cells, with apoptosis ratios of 31.7% and 21.9% at 24 h of treatment at 10 μM in MGC-803 cells. Those two quinazoline derivatives could be considered as useful templates for future development to obtain more potent antitumor agents.