Based on the tunnel effect, a mathematic model was set up to describe the tunnel resistivity of carbon black-filled cement-based composites (CBCC). The relationships between the tunnel resistivity and the microstructure parameters, the motion parameters of carriers as well as the external electric field strength in the CBCC were established by using the model. Furthermore, the inherent relation between the tunnel resistivity and carbon black volume fraction was discovered. Moreover, the effect of carbon black volume fraction on tunnel effect of CBCC was investigated through experiments. The theoretical results obtained from the model were in agreement with the experimental data, which proved the rationality of the tunnel resistivity model of CBCC.