Optical properties of nano-structured ZnO : Sn powders prepared by means of a one-step micro drop fluidized reactor continuously were investigated. The band-gap edge of ZnO : Sn powder was extended to the visible region due to the formation of the extrinsic levels of interstitial oxygen and oxygen vacancy in the band structure of ZnO. The BET surface area of ZnO : Sn powders increased by up to 300%. The fluidization of micro drops of precursors during thermal decomposition contributed to the formation of porous surface morphology and modi flcation of band gap structure of the ZnO : Sn powders by generating micro shear force and strain at the surface of micro drops. The doping of Sn4+ flions into ZnO reduced the electrical resistivity by generating extra free electrons at the surface of ZnO : Sn powders.