Abstract: Rhodamine B(RhB) produces a single scanning polarographic wave at -0.59 V in a 10 mmol/L H₂SO₄ solution. In the presence of PdI₄^2-, RhB⁺ combining with it produces a hydrophobic associacid molecule PdI₄-2RhB via static attraction. By means of hydrophobic force and Van der Waal's force, this associated molecules form (PdI₄-2RhB)_n associated nanoparticles in violet-red color, in size of about 20 nm. The nanoparticles exhibit a synchronous scattering peak at 470 nm and a characteristic resonance scattering peak at 520 nm, and the polarographic wave at -0.59 V is quenched. When organic solvents such as alcohols and acetone is added into the nanoparticle system, the (PdI₄-2RhB)_n nanoparticles are decomposed into PdI₄-2RhB molecules, and the two mentioned scattering peaks disappear, the polarographic wave and the synchronous fluorescence peak increase, and the color of the system reduces to red. The results demonstrate that the formation of (PdI₄-2RhB)_n associated nanoparticles caures the polarographic quenching effect and resonance scattering effect.