Abstract: To study the synthetic method and antibacterial activity of water-soluble fused heterocyclic compounds containing piperazine group, the nucleophilic substitution of 3-(4-chlorophenyl)-6-substituted-s-triazolo-［3,4-b］［1,3,4］thiadiazoles (2a-n) with piperazine in the presence of phase transfer catalyst TBAI afforded 3-(4-piperazin-1-yl-phenyl)-6-substituted-s-triazolo［3,4-b］［1,3,4］thiadiazole and then followed by acid treatment afforded 3-(4-piperazin-1-yl-phenyl)-6-substituted-s-triazolo［3,4-b］［1,3,4］thiadiazole hydrochlorides (3a-n). Twenty-eight new compounds were synthesized and their structures were confirmed by IR, ¹H NMR, MS and element analysis. The in vitro antibacterial activities of all newly synthesized compounds were tested against Gram positive bacteria and Gram negative bacteria with the standard 2-fold agar dilution method. Fourteen title compounds exhibited potential antibacterial activities in vitro. The structures of these compounds needed to be further optimized.