Abstract: Electrical conductivity of carbon fiber reinforced cement composite was measured. The conductivity of the specimens increased by several orders of magnitude while the volume fraction of fibers reached a higher value than the critic concentration. The microstructure associated with electrical percolation phenomena was observed. The influence of fiber volume fraction and fiber length on electrical conductivity and the changing of electrical conductivity under different loading levels were also discussed. The percolation threshold decreases under loading. The relative changing of electrical conductivity both under single loading and under cyclic loading may sensor the stress in elastic, nonelastic, and fracture regions with sensitive response. The results provide an important guide for the manufacture of conductive and intrinsically smart carbon fiber reinforced composites.