The unique chemical properties of nanostructured materials are dependent on the surface thermodynamic properties which depend on the size of nanoparticles. But the quantitative influences of particle size on the surface thermodynamic properties of nanoparticles are not clear completely. In this paper, the relations between surface thermodynamics properties and particle size of nanoparticles have been deduced, and the method of obtaining the surface thermodynamic properties by electrochemistry has also been proposed. Experimentally, the electrode potentials and the electrode temperature coefficients of nano-Ag2O electrodes with different particle sizes were determined at different temperatures. The results indicate that with the size of Ag2O nanoparticles decreasing, the molar surface Gibbs energy, the molar surface entropy and the molar surface enthalpy correspondingly increase. Moreover, when the particle radius exceeds 10 nm, these physical quantities are all linearly related with the reciprocal of average particle radius, and the experimental results are consistent with the theoretical formulas.