Abstract: The kinetics of carbonation leaching of soda-calcined steel slag containing vanadium and rich-calcium as well as a synthetic Ca₂V₂O₇ was studied. The carbonation leaching was done at the temperature range of 15-75℃. The process of carbonation leaching of vanadium from the steel slag is essentially to dissolve calcium vanadate present in the calcined steel slag into the solution in the form of sodium vanadate, and to change calcium into CaCO₃ precipitate. This study has shown that when COpasses through the alkaline leaching solution, Na₂CO₃ is first formed and NaHCO₃ consequently, with the decrease of pH. The process of the solid-liquid reaction may be described by a shrinking core model of dissolution of the particle surface. In the initial reaction period the solution leaching of Na₂CO₃ dominates, but later on that of NaHCO₃ prevailes. The rate of the latter was much faster than that of the former, that is, the rate constant of the leaching reaction k₂>k₁. For the solution leaching of NaHCO₃, the equation of the leaching kinetics was obtained,1-(1-a)^1/3=kτ[C_NaHCO3]^0.46 in which a is the fraction of dissolution of vanadium, k is the rate constant of reaction, min^-1, τ is the reaction time, min, Cis the concentration of NaHCO₃, mol. On th bases of the results of these epxeriments, the mechanism of carbonation leaching of vanadium-containing steel slag has been discussed. This mechanism has also been verified with synthetic Ca₂V₂O₇ sample and an apparent activation energy 25.9 KJ/mol was obtained over the experimental temperature range.