A general effective media (GEM) equation-based scheme is proposed to estimate the relative electrical conductivity of C-S-H gel in this study. It is highlighted that the relative electrical conductivity of the solid phase in cement paste can be treated as a constant only on the iso-degree of hydration basis. On this basis, the relation between the electrical conductivity and capillary porosity of cement paste is fitted by GEM equation to deduce the relative conductivity of the solid phase, as a function of degree of hydration. The relative electrical conductivity of C-S-H gel is estimated from the relative conductivity of solid phase under fully hydrated state (an ideal state), and it equals 0.00775 as estimated.