A new biomimetic catalyst(ML) is formed by the combination of Ce (III, M) and an azacrown ether (1,10-Dioxa-4,7,13,16-tetraaza-cyclooctadecane) in the aqueous solution. The interaction of this complex and DNA is studied with the measurements of fluorescence spectroscopy and gel electrophoresis. The results indicate that ML and calf thymus DNA interacts by the electrostatic interaction mode. Based on gel electrophoresis analysis, the study shows that ML can cleave the circular plasmid pUC19 DNA into nicked DNA under the presence of free radical scavenger, and the cleavage of DNA is a model of hydrolyzed cleavage.