Large　area　uniform　micro-nanostructures　are　fabricated　by　single-beam　femtosecond　laser　ablating　titanium　alloy　Ti-6Al-4V　surface.　These　micro-nanostructuring　metal　surfaces　show　a　great　change　of　their　optical　properties.　Three　significantly　different　surface　structures,　such　as　sub-micron　ripple　structures,　ripple-covered　bulge　structure　and　the　micro-porous　structure,　are　obtained　by　controlling　the　processing　parameters.　These　three　types　of　surface　structure,　which　correspond　to　different　visual　effects,　make　the　titanium　alloy　exhibit　″rainbow-like　color″,　″blue″　and　″black″,　respectively.　The　formation　mechanisms　of　these　surface　structures,　as　well　as　the　roles　of　these　structures　in　changing　metal-surface　optical　properties　are　also　discussed.