The mechanism of the leaching solvents in a leaching operation is discussed. It is concluded that in-situ leaching is a dynamic process involving chemical reactions among multiple phases in which the leaching rate of target metals is dependent on the rate of chemical dissolution as well as on the diffusion rates of reactants and resultants. Based on the theory of dynamical diffusion in multi-phase reactions, a mathematical model is created for metal recovery in leaching. The constitute equations of seepage of solvents and the seepage modelin in the fissured rockmass are deduced under the supposition that the fissured rockmass be considered as a similar continuous medium and the flowing of the fluid in the whole rockmass would obey the law of Darcy.