Abstract: In a phosphate buffer of pH 6.0,the fluorescence intensity of eosin Y (EY) was significantly enhanced by the presence of definite amount of CTMAB when measured at the wavelengths of 316 nm (λex) and 550 nm (λem).Upon addition of an appropriate amount of organophosphorus pesticides (OPP′s),the fluorescence intensity of the EY-CTMAB system was decreased.Linear relationship between the magnitude of decrease in fluorescence intensity and mass concentration of OPP′s in the range of 0.024 to 0.56 mg·L-1,with detection limit (3S/N) of 0.03 mg·L-1.In the test for recovery by standard addition method using samples of rice and soil as matrixes,values of recovery in the range from 90.4% to 100.4% were found,with values of RSD′s (n=5) in the range of 2.61%-4.14%.