To detect the Cu2+ ions in the aqueous solution the detecting system mainly contained three components and two reactions. The components involved are TMB,AgNPs and Na2S2O3 while the reactions are the color reaction due to the oxidation reaction of AG(S2O3)23 and TMB and also the leaching process. TMB and Cu2, ions did not interact to produce a chromogenic reaction. Chromogenic reactions are methods of detection that depend on a change in color occurring during the experimental process to produce both qualitative and quantitative data. S2O32 associated with AgNPs with AgS in the detecting system, and Cu2+ ions may catalyze the leaching process involving S2O32 and AgNPs. The leaching process between S2O32 and AgNPs2, which produced Ag(S2O3)23 and eliminated AgNP s, may be catalyzed by this reaction. TMB might be further catalyzed by Ag(S2O3)23 to become oxTMB, transforming from colorless to blue. The spectra and images from results demonstrate that Cu2+ ions can cause a color change from colorless to blue with high peak at 530nm but no color reaction observed in the Cu2+ free control. However, until now no findings on the catalytic activity of Ag(S2O3)23 with relation to TMB have been made as of yet. The name and molecular structure of coordination compounds formed/involved