The surface structure model of ionic crystal and the equivalent circuit of electrical double layer on the interface of solid electrolyte/vacuum or solid electrolyte/blocking electrode is suggested, taking into account intrinsic disorder of surface layer. In terms of this model the expressions are obtained for surface capacity as a function of potential, temperature and defect concentrations in solid electrolyte. In oxide solid electrolytes from ZrO 2 doped by Y 2O 3, CaO, Yb 2O 3 on the liquid metal droplet (Ag, Sn and CuSn, AuSn, AuCu alloys) near parabolic dependence of double layer capacitance on potential has been established. The minimum capacitance increases exponentially with temperature and decreases in inverse proportion to charge carrier concentration. The minimum capacitance potential coincides within error limits with zero charge potential, which does not depend on temperature; its position is determined by the electrode nature and does not depend on the electrolyte composition. All of these peculiarities agree well with the theoretical conclusions.