This paper deals with the chelate dissolution-differential photometric method for determination of phosporus in calcium superphosphate and rock phosphate samples. A mixed chelate solvent consisting of 15% of citric acid -9% of aluminium nitrate which can control the interference of citric acid and fluorine ion is proposed. The pH value of this mixture solution system is 1.33±0.02. The results obtained has showed that relative error of the chelate dissolution}ifferential photometric methods, as compared with acid dissolution-gravimetric method, is lower by ±1% But for calcium superphosphate with lower phosphorus content, a relative error about ±1.5% is obtained. It is found that the recovery of P₂O₅ added is about 99.0-100.4%.