Abstract: In recent years， researchers have found that the concentration of PCDD/Fs at the outlet of the wet scrubber tower is higher than that at the inlet， and there is a memory effect of PCDD/Fs in the wet scrubber tower. The PCDD/Fs in wet scrubber tower are mainly present in fly ash or adsorbed on polypropylene fillers. The influence of memory effect on the concentration of PCDD/Fs in wet scrubber tower and corresponding measures must be considered in the flue gas purification process of waste incinerator. A wet scrubber tower in a waste incinerator flue gas purification system was taken as the research object， the PCDD/Fs concentrations data at the inlet and outlet of the wet scrubber tower under different working conditions were tested. The influence of memory effect on PCDD/Fs concentration at the outlet of wet scrubber tower under different operation time and discharge mode was analyzed. The results indicated that with the increase of the operation time of the wet scrubber tower， PCDD/Fs would accumulate in wet system， and with the memory effect， the PCDD/Fs concentration at the outlet of wet scrubber tower was higher than that at the inlet. By increasing the amount of sewage discharged of the wet scrubber tower， and regularly changing the water in the cooling and dehumidifying sections of the wet system， the memory effect on the PCDD/Fs concentration at the outlet of the wet scrubber tower could be effectively reduced.