Abstract: Organic phosphorus in UO 2C 2O 4·TRPO complex is converted to inorganic phosphorous with H 2SO 4 HNO 3 H 2O 2 wet cinefaction method. In 0.14 mol/L H 2SO 4 solution containing water soluble polyvinylalcohol as stabilizing agent, the highly sensitive ion associates are formed by the reacetion of basic dye ethyl violet with heteropoly molybdophosphoric blue. Spectrophotometric method is used for determination of phosphorus with these ion associates. The absorbance maximum is at 620 nm. Determination of phosphorus is not affected with mass ratioes R (UO 2 2+ /P) ≤1 4×10 3, R (C 2O 4 2- /P)≤8 8×10 2 and R (C 2O 4 2- /P)≤3 6×10 4 (one time wet cinefaction must be corried out). In aqueous phase, phosphorus can be directly developed and determinated. This method is contrasted with polyvinylalcohol Rodamine B heteropoly molybdophosphoric blue, analytical results are in good coincidence. Conversion ratio of phosphorus is 99.8 %～101.1 %. The minimum detection limit is 0.02 mg/L. The relative standard deviation is 3 %. The recovery ratio is 97 %～103 %.