The co-pyrolysis processes of different proportions of coking-coal, plastic, metallurgical dust (MD) were investigated using thermal analyzer (Setaram Labsys) under a neutral atmosphere of N2 at the sweep rate of 30 mL/min, the linear heating rate and the final pyrolysis temperature were 5 degrees C/min and 1000 degrees C respectively in this study. The experimental results indicated that both the pyrolysis process of coking-coal and that of plastic were radical mechanism. In other word, within the relatively lower temperature range, a large amount of radicals were generated during their pyrolysis processes and stabilized through the intra-radical rearrangement reactions or inter-radical combination reactions. This means that sulfur containing in coal and plastic tends to formed gaseous sulfides, such as H2S, COS, CS2, etc. When co-existing with MD, these sulfides will react with metal oxides containing in MD to form metal sulfide with high stability and the cleaner coke oven gas (COG) were obtained. Within higher temperature interval of 500 degrees C-1000 degrees C, some of the gaseous products after pyrolysis (e.g. H2, CO and C) reinforce the reduction atmosphere that the coking reaction system needs and accelerate the reduction of metal oxides in MD and gasification of metal, which were conductive to the effective removal of sulfur in coke. Therefore, it is definitely feasible to adding waste plastic and MD into coking-coal to remove the sulfur in COG and coke simultaneously.