Abstract: Objective:To develop a label-free fluorescence sensing method for quantitative detection of Ag⁺based on silver ion(Ag⁺)-mediated G-quadruplex conformation switching strategy.Methods:Firstly, the fluorescent dye acridine orange was embedded into the G-quadruplex, resulting in a significantly enhance fluorescent signal.Secondly, when Ag⁺ was added to the system, Ag⁺ could chelate guanine in G-quadruplex, thus inhibiting the formation of G-quadruplex spatial structure to reduce the fluorescence intensity.Finally, the quantitative detection of Ag⁺ was conducted according to the fluorescence intensity change.The fluorescence emission spectra of the samples were analyzed with 480 nm as the excitation wavelength, the fluorescence emission spectra of 500-700 nm were detected, and the fluorescence intensity at the maximum emission wavelength of 525 nm was recorded.Results:The fluorescence sensor designed in this study had a wide linear range(0.1 μmol/L-2.0 μmol/L)and a low detection limit(43.5 nmol/L)for the detection of Ag⁺.In addition, this method achieved satisfactory experimental results in the analysis of recovery rates in complex environmental samples.Conclusion:The Ag⁺ detection method developed in this study has the advantages of simple operation, no need for any fluorescent labeling, low cost, fast analysis speed and good selectivity, and has broad prospects for practical applications in environmental analysis.