As an electrode material, the many excellent properties of nano-Bi2O3 have been researched. However, the influences of particle size on the electrode reaction thermodynamic properties of nano-Bi2O3 electrode are not clear. In this paper, the effect of particle size on electrochemical thermodynamic functions of nano-Bi2O3 electrode was analyzed theoretically. In experiment, the spherical nano-Bi2O3 with different particle sizes and the corresponding nano-Bi2O3 electrodes were prepared, then the temperature coefficients of nano-Bi2O3 electrodes and the thermodynamic functions of the electrode reaction were obtained by measuring the electrode potentials of nano-Bi2O3 electrodes with different particle sizes at different temperatures. The experimental results show that the particle size has significant influence on the thermodynamic properties of nano-Bi2O3 electrode, the standard electrode potentials and the equilibrium constants increase with the particle size decreases, while the temperature coefficient, the mole Gibbs energy change, the mole enthalpy change and the mole entropy change reduce. In addition, these physical quantities are all linearly related with the reciprocal of average particle size when the radius exceeds 10 nm. The experimental regularities are consistent with the theoretical analysis. (C) 2018 Elsevier Ltd.