The slag from steel plants or incinerators was tried to be recycled and be reused as foam materials through plasma arc melting. The study was intended to investigate the making of foam slag with laboratory plasma melting facilities. The investigated materials consisted of different mixtures of Al2O3、SiO2 、FetO、CaO and Na2O, with the fluxes that were necessary to examine the capability of pore-formation in the solidified ingots. It has been found that the foam slag could be obtained with the proper compositions and conditions of arc heating. The dimensions and distributions of pores were studied and correlated with the temperatures and compositions of slag. The results showed that the sizes of pores inside the solidified ingots were in the range of 1~5 mm, and the thickness of slag was around 20 mm. As to the distributions of the pores in the ingots of slag, further improvement would be needed in the future.