Abstract: Solid wastes such as overhauling slag, anode scrap, primary aluminum dross, secondary aluminum dross and smoke dust in the aluminum smelting processes have been listed in the National List of Hazardous Wastes (2021 Edition), which has caused great influences. To analyze the characteristics and environmental hazards of the solid wastes, this study collected samples from electrolytic aluminum industry (EAI), recycled aluminum industry (RAI) and aluminum dross processing industry (ADPI) at different production stages. The phase composition, leaching toxicity and content of heavy metals and fluorides of the samples were analyzed. The results show that the Al, AlN and Al₂O₃ were the typical characteristic phases of primary and secondary aluminum ash. β-Al₂O₃ can be used as a fingerprint feature to identify the process source of primary and secondary aluminum ash. It usually exists in the aluminum ash produced in the process of electrolytic aluminum solution, but rarely exists in the recycled aluminum solution. The contents of heavy metals (Cu, Zn, Cd and Pb) in the waste of EAI were significantly lower than those in RAI and ADPI (P < 0.05). According to the Identification Standards for Hazardous Wastes-Identification for Toxic Substance Content (GB 5085.6-2007), the ratio of accumulated toxic substances of 76.2% of the samples to standard values were ≥ 1, which mean that the total content of accumulated toxic substances exceeded the national standard. Among the 76.2% of samples, 47.6% of samples had the total toxic substance content ≥ 3%, and 14% of the samples had the total carcinogenic substance content ≥ 0.1%. The content of toxic substances was mainly related to heavy metals and fluorides. Fluorides had a greater influence on the content of toxic substances than heavy metals. The fluorides contents of aluminum ash in EAI were significantly higher than that in RAI and ADPI (P < 0.05). According to the national standard GB 5085.3-2007, the over-standard rates of fluorides leaching toxicity of samples from EAI, RAI and ADPI were 60%, 17% and 0%, respectively. The leaching toxicity of fluorides of aluminum ash in RAI was significantly lower than that in EAI and ADPI (P < 0.05). Therefore, the Al, AlN, fluoride and heavy metal were the main environmental risks of hazardous wastes in aluminum smelting industry. It's reactivity of hazardous characteristics was mainly related to Al and AlN, toxicity of hazardous characteristics was mainly related to fluoride and heavy metal. Decreasing the use of fluorine refining agents can be helpful to reduce the toxicity of secondary aluminum ash and environmental risks in aluminum dross processing.