[Objective] The seepage behavior of granite colluvial soil under a low hydraulic gradient was explored，in order to provide a scientific basis for regional engineering construction and geological disaster prevention and mitigation. [Methods] Constant head permeability tests were conducted on granite colluvial soil with varying initial dry densities to analyze its seepage characteristics under low hydraulic gradient. [Results] The relation curves between seepage velocitiy (v) and hydraulic gradient (i) (v-i) of granite colluvial soil exhibits varying degrees of seepage fluctuation under low hydraulic gradients. The permeability coefficient increases with the hydraulic gradient across all dry density conditions. When the hydraulic gradient reached the critical hydraulic gradient (i_cr), the permeability coefficient remained stable and undergoes approximately linear seepage. At this time, the permeability coefficient decreases logarithmically with the increase of dry density. Additionally, under low dry density conditions, the transition in the critical hydraulic gradient fluctuates significantly. However, when the dry density exceeds 1.5 g/cm³, the critical hydraulic gradient (i_cr) increases linearly with dry density. [Conclusion] The saturated seepage behavior of granite colluvial soil under different dry density conditions exhibits fluctuation characteristics under a low hydraulic gradient. The internal mechanism driving these fluctuations is closely related to variations in pore structure. These findings offer a novel perspective on the seepage process of granite colluvial soil and provide a reference for consolidation analysis and seepage stability calculation in engineering applications.