Abstract: This is an article in the field of metallurgical engineering. At present, the cumbersome product routing of FeV alloy causes high energy consumption and hazardous leaching liquor waste. Therefore, a two-step direct reduction to produce FeV alloy from vanadium slags using photovoltaic silicon wafer cutting waste and aluminum ash as reductant, was investigated to solve the above problems. In the present work, the evolution of viscosity and the melt structure during the two-step reduction process of vanadium slags was investigated. The results showed that at 1 873 K, FeO-V₂O₃-Cr₂O₃-MnO-SiO₂-TiO₂-CaO slag system corresponding to the prereduction process, with the decrease of FeO content and the increase of SiO₂ content in the slags, the size of FeCr₂O₄ spinel decreased gradually. The transition of the main influencing factor of the melt structure from FeO to SiO₂ resulted in the increase of structure complexity, the structural complexity of the slag system increased from 0.176 to 2.517, the viscosity of the slag system increased from 0.092 Pa·s to 0.476 Pa·s. FeO-Cr₂O₃-MnO-V₂O₃-Al₂O₃-SiO₂-TiO₂-CaO slag system corresponding to the final reduction process, with the decrease of FeO, Cr₂O₃, MnO, V₂O₃ content and the increase of Al₂O₃ content in the slag, the size of MnCr₂O₄ spinel decreased gradually and the slag system comprised from a solid-liquid mixture to liquid, the transition of the main influencing factor from SiO₂ to Al₂O₃ resulted in the transformation of the main structure of the slag system from silicate to aluminosilicate, the structural complexity of the slag system increased from 0.252 to 2.248, and the viscosity of the slag system increased from 0.091 Pa·s to 0.372 Pa·s.