Abstract: Effects of liquid-solid ratio and time of leaching,residence time of slurry,washing times,elution water volume and filtration rate on the soluble vanadium （SV） content of the residue after acid-leaching of vanadium slag roasted with calcium oxide in the industrial production of vanadium oxides were investigated.It is indicated that the soluble vanadium content in the residual is higher with liquid-solid ratio of leaching lower than 3.6,leaching time more than 240 min,slurry residence time more than 90 min,washing times less than once,elution water volume below 19 m³ and filtration rate exceeding 0. 42 m³/min.A more superior leaching and filtration efficiency can be obtained and the soluble vanadium content in the residual is decreased,with liquid-solid ratio of leaching higher than 3.8,60~150 min of leaching time,3 times of washing,20~22 m³ of elution water volume and 0.25 m³/min of filtration rate.