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.