Transport, thermal and structural properties of the composite solid electrolytes (1 - x)CsHSO4-xSiO(2) (where x = 0-0.8) were investigated. The composites were prepared by mechanical mixing of components followed by heating at temperatures near CsHSO4 melting point (483 K). The dependence of low temperature phase conductivity on x has a maximum with a value 2.5 orders of magnitude higher than that of pure CsHSO4 and conductivity is governed by protons. Heterogeneous doping is shown to change markedly the thermodynamic parameters of the ionic component. The phase transition temperature CsHSO4 in the composites decreases from 414 to 350 K with the increase of the content of heterogeneous additive SiO2 from 0 to 0.7. As x raises CsHSO, the amorphization takes place and the relative change of ionic conductivity at phase transition diminishes, the phase transition becomes diffusive and disappears for the 0.2CsHSO(4)-0.8SiO(2) composite.