Taking 2,6-dichlorophenol (2,6-DCP) as the target pollutant to degrade 2,6-DCP in the background of nitrite (NO2-) coexistence by combined activation of persulfate process by UV and carbon nanotubes (UV/PS/CNTs). The influencing factors and degradation mechanism were investigated, and the cyclic activation potential and by-product generation of the system were investigated. The results showed that the reaction time was 30 min, reaction temperature was 25 ℃, the concentration of 2,6-DCP was 0.05 mmol/L, the concentration of NO2- was 0.2 mmol/L, the dosage of PS was 0.5 mmol/L, and the dosage of CNTs was 50 mg/L, the degradation rate of 2,6-DCP by UV/PS/CNTs system was 95.9%. In this system, the degradation rate of 2,6-DCP increased with the increase of PS and CNTs concentration, and decreased with the increase of NO2- concentration. The solution pH on the degradation of the target compounds showed a trend of increasing first and then decreasing，the degradation rate of 2,6-DCP was 99.8% and 0.3483 min-1 at pH 9.0. CNTs have good recycling performance, and 89.0% of 2,6-DCP could still be removed after 5 repeated experiments, the degradation effect in actual water is good. The mechanism analysis showed that the degradation of 2,6-DCP in this system followed a non-radical oxidation pathway dominated by singlet oxygen, and monochloronitrophenol by-products were generated during the reaction.