The physical and chemical compositions of municipal solid waste (MSW) are important factors affecting the formation and release of polychlorinated dibenzodioxins/dibenzofurans (PCDD/Fs). A 4-year investigation (2017–2020) of the emission characteristics of PCDD/Fs from the flue gas and fly ash by a full-scale MSW incinerator in Ningbo city, Zhejiang province was conducted. This was undertaken to determine the implications of sorting MSW. Results showed that progress made in classifying MSW has led to a significant decrease in the proportion of kitchen waste components, the moisture and chlorine contents of MSW. However, there has also been a significant increase in the proportion of textile and wood components and calorific value. Approximately 60% of the PCDD/Fs generated during MSW incineration were captured in the fly ash that enters the filter bag. The PCDD/Fs emission factors were significantly positively correlated with the proportion of kitchen waste, plastics and heavy metal elements Fe, Ni, Mn, Cr, Pb, Cd, and Zn in the MSW, and negatively correlated with the wet-based high and low calorific values of the MSW. A decreasing trend in PCDD/Fs generation and emission from 3339.3 ng/t MSW in 2018–1787.5 ng/t MSW in 2020 was observed since the implementation of MSW classification as it can reduce the quantity of kitchen waste and plastics, and improve the calorific value of the MSW.