Abstract: To search for fluoroquinolones(FQs)with antitumor activity, the C-3 carboxylic acid group of pefloxacin( 1 )was replaced by fused heterocyclic core, and twelve novel thiazolo［3, 2-b］［1, 2, 4］triazole heterocycles( 6a - 6l )were designed and synthesized. The structures of target compounds were characterized by elemental analysis and spectral data. The results of the in vitro antiproliferative effect on SMMC-7721, L1210 and HL60 cell lines showed that the title compounds exhibited more significant antitumor activity than both of the pefloxacin and the corresponding opening-ring intermediates( 5a - 5l ). Among them, the target compounds which possess a benzene ring bearing a hydroxyl group( 6e )or a fluorine atom( 6j )exhibited more potent antiproliferative effect on SMMC-7721 cells than other compounds. Therefore, the antitumor fluoroquinolones can be designed by replacing the C-3 carboxylic acid group of fluoroquinolones with the thiazolo ［3, 2-b］［1, 2, 4］ triazole moiety.