The　slope　effects　on　the　movement　of　internal　smoke　cannot　be　ignored.　Fire　experiments　in　a　small　scale　tunnel　are　conducted　in　order　to　observe　the　smoke　movement　in　a　tunnel　with　three　kinds　of　slope　(0%,　3%　and　5%)　under　different　longitudinal　ventilation　velocity,　then　find　the　correlation　between　smoke　diffusion　velocity　and　longitudinal　ventilation　velocity,　and　slope　in　tunnel　by　numerical　fitting　and　dimensional　analyses,　finally　conclude:(1)　as　longitudinal　ventilation　velocity　increases,　smoke　diffusion　velocity　gradually　decreases;　(2)　when　longitudinal　ventilation　velocity　is　smaller,　with　the　increase　of　slope,　smoke　diffusion　velocity　is　gradually　increasing;　(3)　when　longitudinal　ventilation　velocity　is　large,　slope　to　smoke　diffusion　velocity　is　not　affected.　These　quantitative　conclusions　provide　fire　Prevention　of　the　tunnel　in　city　with　a　reference.