3,6-Diaminocarbazole derivatives were synthesized and their structures were confirmed by 1H NMR, 13C NMR and ESI-MS. Their DNA binding properties were investigated by UV-Vis, fluorescence and circular dischroism (CD) spectroscopies and thermal denaturation experiment. Results show that all the 3,6-Diaminocarbazole derivatives are to intercalate into and can acrt as intercalating agent of Ct-DNA.