The multi-armed US architectures can be synthesized from the reaction of the anhydrous CdCl2 and sulfur powders in ethylenediamine, in which a simple one-step reactant-solvent synchronous (RSS) co-assisted effect was proposed to be responsible to the growth of the multi-armed structures. The as-prepared products were characterized by XRD. XPS and TEM. In addition, their optical properties were also shown by UV-vis and fluorescence spectrum. FT-IR spectrum indicated that the dissociation of ethylenediamine molecule absorbed on the surface of US resulted in the formation of intermediate CdS(en)(mn) cores and thus provided the condition for the anisotropy growth of US. The present technique may give a clue to grow the one-dimensional nano-sized semiconductors by the proper choice of the reactant and the solvent. (C) 2005 Elsevier Ltd. All rights reserved.