Binding effect of the antitumor dirhodium (II) compounds to the plasmid pUC19 DNA has been studied under different molar ratio of Rh (II) compounds to base pair of pUC19 DNA (Rf) and time. The electrophoresis results indicate that Rh binding affect the DNA conformation and therefore, Rh-DNA migrated in the different position comparing with native DNA. At high value of Rf ICP-MS (Inductively Coupled Plasma Mass Spectrometry) measurement confirmed that 46% of Rh binds to DNA. In vitro result shows that DNA synthesis was inhibited by the Rh binding.