Clusters of the WN_n ( n = 1–9) forms are investigated theoretically using density functional theory methods. Geometry optimizations are undertaken under the constraint of well-defined point-group symmetries at the (U)B3LYP level employing a pseudopotential method in conjunction with double-zeta basis sets for W atom and 6–31G(d) basis sets for N atoms. In this article, different molecular properties such as total energies, relative stabilities as well as chemical bonding and equilibrium geometries of WN_n ( n = 1–9) clusters are systematically calculated and discussed. Theoretical results show that the lowest-energy WN_n ( n = 1–9) isomers prefer to interact with N₂ units to N₃ and N units, moreover, some circle-like low-lying stable WN_n structures are considered, which turn out to be less stable than isomers with N₂ units as the building blocks, furthermore, W atom is in favorable of chemisorption nitrogen rather than dissociative nitrogen, which is in good agreement with experimental observation. Comparisons theoretical results on geometry and stretching frequency with available experimental and theoretical data are made, a good agreement is obtained. In addition, natural population analyses are calculated in order to elucidate the charge distributions in the clusters.