Highly ordered metal Sn nanodot arrays were prepared by vacuum electron beam evaporation using porous anodic alumina (PAA) membrane as the substrate. They were characterized by means of scanning electron microscopy (SEM) and X-ray diffraction (XRD). SEM images indicated that the Sn nanodot arrays are highly ordered and coincid with the contours of porous anodic alumina. The shape of Sn nanodot is spherical and the diameter approximates the pore diameter of the PAA membrane. XRD showed that crystallographic structures of Sn nanodot arrays are the same as the bulk Sn. The forming process and mechanism of the Sn nanodot array was discussed.