To establish a method for nitrite-UV spectrometry determination of free chlorine in drinking water. Methods 1.0 ml sodium nitrite solution (ρ=5 g/L) was added into water sample containing free chlorinerole, reacted for 30 min, and added 1.0 ml sulfamic acid solution (ρ=10 g/L) and 1.0 ml hydrochloric acid (C=1.0 mol/L). Samples were detected for absorbance value at 220 nm wavelength with nitrate nitrogen as standard, and free chlorine content was calculated. Results Sodium nitrite was quantitatively oxidized by free chlorine into nitrate which showed an equimolar relationship (r=0.999 8). Sulfamic acid eliminated the influence of excessive nitrite. This method could be applied for direct determination of water sample at room temperature.The limit of quantification was 0.05 mg/L with RSD 1.43%～10.00%, the recovery was 94.23%～103.20%. Conclusion This method could be used for the determination of free chlorine in drinking water.