Abstract: The composition of ferrovanadium smelting slag is mainly controlled by adjusting CaO addition during the ferrovanadium production. The addition amount of CaO will affect the physical and chemical properties of the slag at high temperatures,the occurrence state of vanadium and total vanadium（TV）content in the slag.In this work,the effect of slag composition on TV content and occurrence state of vanadium in ferrovanadium smelting slag was investigated.The results show that TV content in the slag decreases as basicity reduces,from 3.01% to 2.39% respectively at 0.22 and 0.13 of basicity.Vanadium is principally hosted in magnesia-alumina spinel of the slag with higher basicity while in corundum and magnesia-alumina spinel of the slag owning lower basicity.The main species of vanadium in ferrovanadium smelting slag is V³⁺,and Mg O content is the key factor influencing TV content in the slag.The appropriate composition for the slag is 3% ~5% of Mg O and 10% ~12% of CaO.