Abstract: The influence of municipal sewage sludge (MSS) on the discharge of PCDD/Fs in the process of munici-pal solid waste (MSW) combustion is discussed. The co-incineration tests of MSW and MSS (0%, 5%, 10% and 15%, respectively) were carried out in a MSW incineration in southern China in May 2016 (wet season) and Jan 2017 (dry season). The PCDD/Fs were mainly distributed in flying ash in the wet season and in the slag in the dry season. The emission of PCDD/F per ton of raw material after incineration was 14.1~29.2 μg TEQ /t higher than that in the raw material in the wet season and was 9.2~9.9 μg TEQ /t lower in the dry season. The PCDD/Fs congener profiles were dominated by 2, 3, 4, 7, 8-PeCDF (13.0%~72.1%) in the output discard in both seasons, which can be attributed to the decomposition and recombination of PCDD/Fs. The added MSS during MSW co-incineration represses the production of PCDD/Fs due to the higher ratio of sulfur to chlorine in the incineration materials. Therefore, MSS can be an ideal candidate for MSW disposal under appropriate management.