Abstract: Abstract The resistivity of cement specimens under different pressures was studied. The specimens are mixed with carbon fibres. The results show that when pressure gets larger and larger, the resistivity of specimens changes.This process can be divided into three parts:reversible sensing period, balance period and sharp increasing period. These three periods respectively show the closure opening of original cracks, the embryo of new flaws and def,cts extending to failure. The conducting mechanism is also analyzed. The characteristic of carbon fibre cement can be used in the non-destructive detection of concrete dams etc.