Abstract: A new method for the prediction of adsorption equilibria of a multicomponent liquid mixture on heterogeneous solid surfaces is proposed on the basis of the lattice model.Equations for adsorbed-phase activity coefficients are obtained by taking the energetic heterogeneity effects of solid surfaces into account.Only the binary parameters are needed for the calculation of the equilibrium of multicomponent adsorption.The adsorption equilibria of benzene-toluene-cyclohexane on silica gel,benzene-ethanol-cyclohexane on activated carbon and benzene-ethyl acetate-cyclohexane on activated carbon are calculated by the method and the theoretical results agree well with the experimental data.