RF thermal plasma systems for treatment of fly ash have been proposed in order to recover the useful metals and materials from fly ash discharged from a melting furnace. The fundamental investigations for recovering the detoxified and useful materials from fly ash by means of RF thermal plasma process were performed. In terms of the numerical analysis and the experimental results, it is verified that fly ash is decomposed by RF thermal plasmas and heavy metal species separate from fly ash by means of the effects of temperature control and hydrogen.