Our previous research have identified a series of N-phenyl substituted isatin derivatives as antitumor agents in vitro. 5-Bromo isatin derivatives have been found to increase their cytotoxic activity and selectivity. A series of 5-bromo-N-phenyl isatin analogues were designed and synthesized about 40-80% overall yields. All of synthesized compounds have not been reported before. Their structures were characterized by 1H and 13C NMR. The cytotoxic activities of all the synthesized derivatives were evaluated against two human tumor cell lines HepG2 and HT-29. Results showed that all bromo-substituted compounds exhibited potential anti-tumor activities against HepG2 and HT-29.