Three different scale color graphics (white,gray,black) on Al99.7 aluminum surface can be obtained by tuning the Nd∶YAG pulse laser marking parameters.In order to study the mechanism of laser blackening,the spectral reflectivity of the samples was measured by spectrophotometer.The surface marked by the laser was analyzed by scanning electron microscopy and energy dispersive spectroscopy.It was found that the change rule of gray scale was consistent with that of the spectral reflectivity,but the microscopic morphologies are different greatly,and surface reflectivity of the sample with micron-scale pores and nano-scale floc is the lowest and its color is the deepest.The results show that the micro- and nanoscale structure on the surface induced by laser energy can reduce spectral reflectance within the visible range,and it is the main reason for marking graphs to appear color.