This research was designed to investigate the formations of hazardous air pollutants in the MSWspyrolysis-gasification-melting process. In this survey, PCDs/PCDFs (polychlorinated dibenzo-p-dioxins andpolychlorinated dibenzofuran) were investigated in the two facilities (A and B facilities). In A facility, the3 respectively on the secondary incinerator, boilerand stack. In B facility, the PCDDs/PCDFs concentrations were 0.2, 0.05 ng I-TEQ/m3 respectively on thepyrolysis-gasification-melting furnace and stack. The concentrations of PCDDs/PCDFs increased due to resynthesisduring cooling process in the both facilities. High concentrations of PCDs/PCDFs isomers were founded as2,.3, 4, 7,.PeCDF, 1, 2, 3,.7, 8-PeCDD and 2, 3, 4, 6, 7, 8-HxCDF orderly in B facility.