We report on the growth of self-assembled GaN nanowires (NWs) on Si(1 1 1) substrates via pulsed metal-organic chemical vapor deposition (MOCVD) technique. Au colloid nanoparticles dispersed on Si(1 1 1) substrate were used as catalyst to conduct the GaN NWs growth. The size of the GaN NWs can be tailored by an easy and simple method of optimizing the Au colloids catalyst using Ga pre-deposition. The pulsed MOCVD growth mode was used to grow GaN NWs in which the group III and group V precursors were introduced alternately in the sequence. The surface morphology and optical characterization of the grown GaN NWs were studied by field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), photoluminescence (PL), and cathodoluminescence (CL). The XRD pattern confirmed the hexagonal structure of GaN NWs. The experimental results indicated that the GaN NW diameter depended on the size of AuGa droplets. The pulsed method combined with growth temperature considerably affected the shape and density of the GaN NWs. © 2011 Elsevier B.V.