Abstract: In 0.01 mol/L HCl medium, PtI₆^2- and I^- combine to PtI₆^2-. PtI₆^2- reacts with citirizine(CTRZ) to form (CTRZ-PtI₆) association molecule.The molecules aggregate automatically, owing to strong hydrophobic and molecular forces. (CTRZ-PtI₆)_n association nanoparticles in violet-red color were observed.It exhibits three resonance scattering peak at 310 nm, 400 nm, 610 nm, and there is a synchronous scattering peak at 470 nm. The absorption values all increase in the wavelength of 350～740 nm.Under the conditions chosen, the CTRZ concentration in the range of 0～10 μg /mL is linear to the A_580nm value.The mole absorption coefficient ε_{580 nm} is 1.30×10⁴ L/(mol·cm).The results shown that the formation of (CTRZ-PtI₆)_n association nanoparticles produce the resonance scattering effect, and it is in violet-red color.