Abstract：There exists distinct fluid-solid coupling effect during seepage in low permeability rock. Experiments upon sandstone from Changqing oil field are performed with FDES–641 triaxial system to investigate the laws between the permeability of rock and the effective pressure. It is proved by experiments that the permeability of rock will drop regularly along with the increasing of the effective pressure. With the increasing of effective pressure，the permeability of rock decreases. The variation relation between them can be described by quadratic equation. When plot curve in the reference frame with X-axis to be the effective pressure and Y-axis the permeability of rock，an inflexion of the curve exists. Before reaching the inflexion，the permeability of rock will drop more quickly but after the inflexion such dropping will become more gentle. The location of inflexion in curve will vary for different rocks. The coupling mechanism of seepage in rock mass has not been completely made clear so far；and the coupling factors affecting the permeability of rock are actually too complex to describe one by one. The coefficient of sensitiveness between the permeability of rock and the effective pressure is defined accordingly as to generalize these factors. Such coefficient can evaluate the changing trend of the permeability of rock related to the effective pressure. The higher the coefficient is，the bigger amount the permeability of rock will change along with the effective pressure. By the way the effort to determine the value of permeability can shift to find out the coefficient of sensitiveness. According to the numerical fitting result of experiments，the relation between the coefficient of sensitiveness and the effective pressure can be described by exponential function. The expression between the permeability of rock and the effective pressure is deduced based on the conception of coefficient of sensitiveness.
