To make clear the reason for high De-HCl efficiency in RDF fired fluidized bed combustion in spite of high combustion temperature, combustion tests of RDF were carried out in an electric furnace and the De-HCl characteristics versus calcium added to the RDF were investigated. The following results were obtained: (1) De-HCl efficiency was more than 85% for three samples which were each produced by different processes, and which had different amounts of calcium added. (2) De-HCl efficiency became higher at low heating temperature and it was about 95% at 600 degrees C.