In the medium of 0.14 mol·dm^-^3 H~2SO~4, PO~4^3^- and MoO~4^2^- react with rhodamin S to form an associated complex of PMo~1~2 heteropoly acid-rhodamin S, which exhibits a sensitive resonance scattering peak at 610nm. Phosphorous concentration in the range of 0.2120μg·dm^-^3 is linear to the intensity of resonance scattering light. The results show that this method has high sensitivity and good selectivity. This method has been applied to the analysis of phosphorous in water and tea samples. The analytical results are in agreement to those of oscillopolarography. This work demonstrates that the primary cause of exhibiting resonance scattering peak is the formation of unsoluble associated complex and the big size sol.

Key words: PHORSPHORIC ACID, MOLYBDIC ACID, HETEROPOLYACID