The percolation rule of fluids in low-permeability reservoirs is the important research field for seepage mechanics．Low permeability reservoirs are characterized by low permeability，fine pore for the oil and water flowing, high fihrational resistance and significant interactions between the solid-liquid interface and liquid-liquid interface． which results in the complexity of the percolation rule．Based on the core flow test，the effects of injection pressure on rock permeability and percolation rules of liquids are analyzed．The result shows that low perm eability reservoirs have the characteristic of non-linear fluid flow through porous medium．The fluid flow speed in the core changes very little with the pressure gradient when the injection pressure is relatively low．It means that the injected water is dificult to enter the formation．When the pressure gradient is larger,there exists all approximate linear relation between flow speed and pressure gradient．Under the condition of invariant overlying pressure and pressure gradient，the higher the injected pressure gets，the higher the perm eability of rocks is．It shows that high pressure water injection will enhance the water injection eficiency under the precondition of the reservoir formation protection．