We designed a facile thermal conversion route to synthesize 2H-WS 2 nanoflakes using different tungsten oxide nanorods and S powder as starting reaction reagents. Various sizes and dimensions of nanoflakes with very regular hexagonal outer shapes and smooth surfaces were obtained by using different tungsten oxide nanorods such as W 18 O 49 and WO 3 as precursors. The structural properties and formation mechanisms of the 2H-WS 2 nanoflakes were systematically investigated. It is found that both the size of tungsten oxide nanorods and reaction temperatures play crucial roles in the formation of regular hexagonal WS 2 nanoflakes. These results may give a new insight to the syntheses of other layer-structural MX 2 nanotructures (M=transition metal, X=S, Se).