The　axial　concentration　distribution　of　both　particles　with　better　wetting　(forming　non-attached　system)　and　poorer　wetting　(forming　attached　system)　was　investigated　in　a　vertical　gas-liquid-solid　fluidized　bed　of　4.2　cm　in　diameter　and　130　cm　in　height　with　the　solids　holdup　less　than　0.05.　The　one-dimensional　sedimentation-dispersion　model　could　be　used　satisfactorily　to　describe　the　axial　distribution　of　solids　holdup　by　modifying　only　a　model　parameter,　i.e.　by　means　of　the　terminal　settling　velocity　minus　a　certain　value,　which　is　a　function　of　gas　velocity　and　considers　the　effect　of　an　additional　drag　force　resulted　from　attached　rising　bubbles.　The　axial　profiles　of　solid　concentration　predicted　are　in　good　agreement　with　experimental　results.　This　model　also　explains　reasonably　the　different　axial　distributions　of　solid　concentration,　i.e.　the　solids　holdup　decreases　as　the　axial　height　increases　in　non-attached　system,　but　increases　with　the　axial　height　in　attached　system　at　a　given　gas　velocity.