Abstract: To achieve simple, rapid, and highly sensitive quantitative detection of estradiol in water body, using aptamer as the recognition element for estradiol and Rhodamine B as the signal molecule, an aptamer sensing method for quantitative detection of estradiol in water body was developed based on the fluorescence quenching effect of gold nanoparticles on Rhodamine B. Gold nanoparticle solution was synthesized by the trisodium citrate reduction method using chloroauric acid. The 250 μL of gold nanoparticle solution and 50 μL of 10 μmol · L^-1 aptamer solution were added into 50 μL of filtered lake water sample. After mixing well, the mixed solution was incubated at 25 ℃ for 20 min. Then, 125 μL of 1.00 mol · L^-1 sodium chloride solution and 25 μL of 40 μmol · L^-1 Rhodamine B solution were added. The mixed solution was mixed thoroughly, the volume of which was supplemented to 500 μL with water. After incubating for 5 min at 25 ℃, the fluorescence intensity difference ΔF(the difference between the test group and the blank group) was measured at an emission wavelength of 574 nm under an excitation wavelength of 530 nm. Quantitative detection was performed using the linear relationship between ΔF and estradiol concentration. It was shown that the linear range of this method was 20-200 nmol · L^-1, with detection limit (3s/k) of 10 nmol · L^-1. For lake water samples spiked with 20, 50, 100 nmol · L^-1 of estradiol, the recoveries were found in the range of 87.0%-102%, giving RSDs (n=5) of the determined values in the range of 2.8%-4.9%. In the fluorescence system, the addition of interfering substances (estriol, chlorothalonil, and 4-hydroxychlorothalonil) resulted in minimal changes in fluorescence intensity.