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• The presence of salts influenced negatively properties of fired brick. • Desalination is required for the reuse of fly ash in brick production. • Chemically bonding forms of heavy metals changed after firing. • Leaching of heavy metals below regulation standards. The introduction of municipal solid waste incineration fly ash (MSWIF) during manufacturing process of fired bricks is a promising disposal method. However, the quality of products is negatively reduced and environmental risk increased significantly with the addition of MSWIF. This study proposed a novel approach to enhance the quality and environmental safety of fired brick by adding electric arc furnace slag (EAFS) as the pore plugger, which could overcome disadvantages brought by the introduction of MSWIF. Results showed that linear shrinkage and bulk density increased with the addition of EAFS, while water absorption and apparent porosity are reduced by more than 50%. The fracture microstructure of fired brick changed from porous to smooth with the addition of EAFS. The thermal conductivity declined by 25% and 30% at 1050 and 950 °C, and compressive strength was enhanced by 50% with the addition of 30 wt% EAFS. The chemically combination reactions between raw materials, such as the formation of albite, are promoted remarkably with the addition of EAFS. The leaching concentrations of heavy metals are far lower than regulatory limitations and environmental safety are enhanced significantly. In all, the addition of EAFS can promote the quality and environmental safety of fired brick, and can be used as an effective way to solve problems caused by introducing heavy metal solid waste. [ABSTRACT FROM AUTHOR]