The electrochemical properties on solid particle surfaces in an aqueous system have found wide application in many fields. However, for some of them there are no reliable methods of determination. What is particularly worth mentioning is the surface potentials of solid particles. Though this is a most important property and a most basic parameter in colloid interface electrochemistry, no reliable method for its determination is available yet. In the present paper, based on the diffuse double-layer theory, mathematical relations are constructed between the average concentration of ions positively adsorbed in the diffuse double layer and the surface potential of solid particles, thus transforming the determination of surface potential of solid particles into that of the average concentration of ions in the diffuse double layer, and then by applying the standard relationships of Gouy-Chapman theory, the mathematical relations of the average concentration of ions in the diffuse double layer with surface charge density, electrical field strength at surface, and specific surface area of solid particles are constructed. (C) 2004 Elsevier Inc. All rights reserved.