Abstract: To investigate the nonlinear behavior of seepage flow in fractured rock, a supplementary device to the MTS815.02 Rock Mechanics Testing System was designed. This paper presents the testing principle and scheme, the testing configuration, the approach to processing the testing data and some test results. Statistical indices of percolation properties of every group of rock specimen are calculated. The regressing relation of k (generalized permeability), β (the β factor of non-Darcian seepage flow) and axial strain of fractured rock is presented. It is concluded that the relation between the statistical indices of percolation properties of fractured rock and axial strain can be expressed by quadratic polynomial, and the variance coefficient of percolation properties decreases as the axial strain increases.