According to the properties of 'HPLC-6' that within the interfacial region of ice and water, we have calculated the fraction of ice crystal surface covered by the protein. The relationship between the fraction and the solution concentration is given. The additional pressure resulted from the change of surface curvature due to adsorbed HPLC-6 that on the ice crystal surface is derived by Laplace equation. Based on the first order Gibbs-Thomson equation, a quantitative calculation on the thermal hysteresis activity of the protein is obtained. The theoretical results are consistent with the experimental data. (C) 2003 Elsevier B.V. All rights reserved.