<p>Glacial deposits are Quaternary sediments with broad particle-size gradation, resulting from glacial erosion, transport, and deposition. Their permeability characteristics differ notably from those of other Quaternary sediment layers. Accordingly, this study collected glacial deposit samples from the upper reaches of the Yi’Ong Zangbo River in Tibet and analyzed the permeability characteristics and seepage-induced internal instability of glacial deposits under various hydraulic loading paths, using 5 sets of undisturbed upward seepage experiments. Hydraulic conductivity strongly correlates with loading path, while eroded fines accumulation is governed by <i>d</i>_15<i>c</i>/<i>d</i>_85<i>f</i>. The seepage-induced internal instability process can be divided into 3 distinct stages: initial seepage, suffusion, and internally instability. The hydraulic gradient equation at the onset of suffusion was derived from erosion rate and <i>d</i>_15<i>c</i>/<i>d</i>_85<i>f</i> indicators. Additionally, the erosion resistance index, calculated from the dry mass of eroded fine particles and dissipated energy, indicates that glacial deposits are generally highly erodible, with erosion resistance improving as <i>d</i>_15<i>c</i>/<i>d</i>_85<i>f</i> decreases.</p>