The Gibbs model of surface tension, together with the approach by Defay and Prigogine [Surface Tension and Adsorption (Longmans, New York/London, 1966)] and Dufour and Defay(1,2) [Thermodynamic of Clouds (Academic, New York/London, 1963)] for calculation of the Gibbs adsorption Gamma, is used to estimate the curvature effect on ice surface tension. For the case of the ice-water interfaces a new model for calculation of the Gibbs adsorption Gamma(i/w) is proposed. Ice surface tension decreases with the curvature which in turn reduces the equilibrium radius of an ice embryo thus making the nucleation event more probable. The comparison of the calculated transitional region between ice and supercooled water with that obtained from experiments and theoretical calculations showed that the proposed new model gives the correct sign and correct order of magnitude for Gamma(i/w).