The recycling of waste plastics that include chlorine-containing plastics, such as polyvinyl chloride, is difficult because that cause the equipment corrosion. Then, the melt process mixed with polyvinyl chloride (PVC), polyethylene, polypropylene, polystyrene, coal tar (HOB) and Fe2O3 as the antichlor agents were examined to stabilize chlorine that was detached from PVC to form iron chloride. It was resulted that organic chlorine compound besides the iron chloride might be generated. After the chlorine behavior on melt process was analyzed, the following results were obtained; (1) HCl eliminated from PVC is formed FeCl2·2H2O and FeO (OH, Cl) or physically captured by HOB on the melt process. (2) Organic chlorine compounds maybe formed by the addition reaction of HOB with HCl. Therefore, stabiliz-ing HCl as a metallic chloride decreases the generation of organic chloride compounds. (3) It is necessary to obtain high metallic chloride yield that some HOB is added for physically capturing. At the same time, it is effective that the Fe2O3 addition ratio is raised because the contact probability with chlorine is raised.