Abstract: Potassium persulfatc was used as photo-oxidant in this experiment.Organic nitrogen compounds in aqueous solution can be quantitatively decomposed within 25 minutes by two steps of (acidic and alkaline) UVirradiation. Results show that the quantitative recovery of the nitrogen compounds with C-N, O-Nand N-Sbonds can be obtained, while the nitrogen compounds with N-Nand N=Nbonds form gaseous nitrogen during the photolysis.Under the condition of pHover 9.4, nitrates are reduced to nitrites under UVirradiation. The total nitrogen content can be determined in the form of nitrite directly after photolysis. The cadmium column commonly used lor the nitrate reduction is therefore saved.