Information about the heavy metals release from industrial solid wastes is important for more reliable management of their environmental hazards. This study was conducted to investigate the effect of tissue of solid waste on the release of heavy metals from the steel smelting plant. After the investigation at the Khazar steel smelting (KSS) plant in Guilan province, its waste type, source, quantity and quality were characterized. The major wastes generated from the KSS plant were characterized to be the slag, furnace dust, and spent refractories. KSS solid wastes contained heavy metals in varying amounts, with the ranges of 1500-2200, 80–114, 6172-11100, 88-82, 48-29, 56-60, 4-14, 144-370 and 0.9-1.0 mg/kg−1 for Mn, Cu, Zn, Ni, Cr, Co, Cd, Pb and As, respectively. The concentration of the iron was high in these wastes (109900-672000 mg/kg−1). The results confirmed the high concentration of heavy metals except for Arsenic. The TCLP results of the KSS dust and slag showed the almost all the heavy metals concentrations by the leaching test were lower than the detection limits except Fe (524.5-187.6 mg/kg-1) and Mn (14-10.10 mg/kg-1). According to the results, all the wastes generated by the KSS plant were reusable and recyclable.