Abstract: The irradiated TBP extraction system is separated by distillation, extraction and silica gel chromatography. The Ru retentions by the resulted fractions were determined. The species that retain Ru most are regarded as main complexing agents. The main complexing agents that can coordinate with Ru were identified by infrared spectrophotometer, element analysis, gas chromatography-mass spectrometry and liquid chromatography-mass spectrometry. Nitrous acid ester containing organophosphates are the main complexing agents that can coordinate with Ru. They are responsible for Ru retention. The compounds C₁₂H₂₈O₈P₂, C₈₁H₁₇₁N₂O₃₂P₇, and C₇₈H₁₆₁NO₁₈P₄ are deduced to exist in the complexing agents.