The fluorescence characteristics of sulfasalazine（SASP） oxidized by potassium permanganate in sulfate acid medium were studied.The result indicated that SASP can react with potassium permanganate in sulfate acid medium to produce a strong fluorescent species（λex=301 nm，λem=366 nm）.Based on this phenomenon，a novel on-line oxidizing fluorescent method combined with flow injection technique was established for the determination of SASP.The experimental conditions affecting the fluorescence intensity of the system were investigated.The optimized experimental conditions were as follows: potassium permanganate concentration: 2.0×10-3 mol/L; sulfate acid: 2.0 mol/L; flow rate: 1.2 mL/min; length of mixing tube: 50 cm.Under the optimal experimental conditions，the calibration curves were linear in the range of 1.2×10-5-2.0×10-3 g/L with detection limit of 3.0×10-6 g/L.The relative standard deviation（RSD，n =11） was 0.6% for the determination of 1.2 ×10-4 g/L SASP standard solution.The proposed method had the advantages of simplicity，rapidity，high sensitivity and selectivity，and was successfully applied in the quantitative determination of SASP in enteric coated tablets with recoveries of 96%-107%.