The leaching kinetics of niobium from a low-grade niobium-tantalum ore by concentrated KOH solution under atmospheric pressure has been studied. Significant effects of reaction temperature, KOH concentration, stirring speed, particle size and mass ratio of alkali-to-ore on the dissolution rate of niobium were examined. The experimental data of the leaching rates and the observed effects of the relevant operating variables were well interpreted with a shrinking core model under diffusion control. By using the Arrhenius expression, the apparent activation energy for the dissolution of niobium was evaluated. Finally, on the base of the shrinking core model, the rate equation was established.