A new ternary copper(Ⅱ) complex: ［Cu(TBZ)(L-Ala)(H₂O)］ClO₄［TBZ=2-(4′-thiazolyl) benzimidazole, L-Ala =L-alaninate］, was synthesized and characterized by elemental analysis, molar conductivity, infrared absorption spectrum, and electronic absorption spectrum. The complex was assayed against gram-positive(Staphylococcus aureus, Bacillus subtilis) and gram-negative(Salmonella typhi, Escherichia coil) bacteria by double dilution method, and the interaction of the complex to DNA was investigated by electronic absorption spectrometry, fluorescence spectrometry, CD spectrometry, viscosity measurement and agarose gel electrophoresis. The results indicated that the complex had good antibacterial activity, which could be bound to CT-DNA (calf thymus DNA) by intercalative mode, cleave pBR322 DNA in the presence of vitamin C in the involvement of the hydroxyl radical, and possibly singlet oxygen.