The　human　behavior　of　walking　upstairs　was　studied　by　field　measurement　in　a　10-storey　building,　which　simulates　the　greatest　depth　of　most　underground　facilities.　The　effects　of　age,　gender,　walking　distance,　and　fatigue　on　individual　free　ascending　speed　on　stairs　were　investigated.　The　experimental　results　showed　that　walking　distance　and　fatigue　due　to　the　long-distance　upward　walking　have　great　impact　on　the　upward　walking　and　ascent　speed.　When　climbing　over　8　floors　(vertical　height　about　30　m),　the　mean　ascent　speeds　were　0.97　m/s　and　0.78　m/s　for　young　males　and　females,　and　0.91　m/s　and　0.68　m/s　for　middle-aged　males　and　females,　respectively.　The　mean　ascending　speed　that　is　used　to　predict　the　evacuation　time　should　be　combined　with　the　traveling　distance　or　floor　levels.　Ascent　speed　models　for　males　and　females　walking　along　a　medium-long　stairway　were　developed　to　describe　the　fatigue　effect　on　ascending　speed　based　on　the　vertical　heights　travelled.