Abstract: DNA-templated Au nanoclusters (DNA-AuNCs) are synthesized by using A30 DNA as thetemplates. The obtained DNA-AuNCs possess a maximum excitation wavelength at 290 nm and a maximum emission wavelength at 475 nm. In the presence of 4-nitrophenol, the fluorescence signal of DNA-AuNCs is significantly quenched by the inner filter effect, due to the UV absorption spectrum of 4-NP overlaped partly with the fluorescence excitation and emission spectra of DNA-AuNCs. A novel fluorescent strategy is developed for the sensitive determination of 4-nitrophenol (4-NP) based on the DNA-AuNCs inner filter effect (IFE) induced fluorescence quenching. The method exhibits good linear relationship with 4-NP concentrations in the range from 1~80 μmol/L with the limit of detection of 0.3 μmol/L (R_SN=3). In addition, the method is successfully applied for the determination of 4-NP content in lake water samples.