Binding properties of a nickel complex, [Ni(phen)(pha)(H 2 O) 3 ] (phen=1,10-phenanthroline, pha=o-phthalate) to DNA were comprehensively investigated by electronic absorption spectroscopy, viscosity, electrochemistry, melting temperature and gel electrophoresis measurements. After interaction with DNA, the hypochromism and bathochromism for the characteristic absorption peaks of [Ni(phen)(pha)(H 2 O) 3 ] revealed a typical intercalation, which was proved by viscosity and melting temperature experiments. Electrochemical assays showed that the electrochemical activity of the nickel complex was shielded after inserting into the double-helix structure of DNA. Moreover, the results of agarose gel electrophoresis showed that the complex had moderate cleavage ability to supercoiled DNA in the presence of H 2 O 2 .