According to the properties of type III antifreeze protein (AFPIII) within the interfacial region of ice and water, the theoretical model of the large ligands binding on one-dimensional homogeneous lattice have been extended to two-dimensional lattice-like surface(ice surface). By using of this two-dimensional model, the fractions of the ice crystal surface covered by two type AFPIII variants that have different ice-binding face are calculated respectively. The thermal hysteresis activities of these proteins are obtained. The theoretical results are agreement with the reported experimental data.