Abstract: Conglomerate reservoirs have several characteristics, such as high gravel content, complex modal and quasi double porous structures.According to preliminary studies, due to the existence of gravel seam, nonlinear seepage characteristics can be observed during the development of water flooding.In this paper, one-dimensional and three-dimensional physical models of typical conglomerate were designed, multi-stage flow rate water flooding experiments were conducted.Through the comparison with sandstone cores, it is verified that the existence of gravel seam is the main factor that leads to stress-sensitive nonlinear seepage; it has a significant effect when the pressure gradient and the injection speed reach a certain value.Additionally multi-directional pressure is another necessary condition for gravel seams’ open.This is caused by gravel edge seam open and the same interpretation can be found in well testing.It provides a scientific fundamental for optimizing the parameters in waterflooding and polymer flooding of conglomerate reservoirs.