A precursor to prepare nanocrystalline Cu2-xSe was obtained in the solvothermal reaction of CuCl2. 2H(2)O with elemental selenium at 140 degrees C for 10 h in ethylenediamine (en). Powder X-ray diffraction (XRD), infrared (IR) spectroscopy, thermal analyses (TGA-DTA), and inductively coupled plasma (ICP) analyses showed that the precursor could be a complex with the form Cu2-xSe(en)(2), which released the ligand ethylenediamine to obtain Cu2-xSe crystals by pyrolysis or protonation. XRD, transition electron spectroscopy (TEM), and X-ray photoelectron spectroscopy (XPS) were used to investigate the phase, size, morphology, and composition, respectively, of the final product. The analyses indicated that it was a pure nanocrystalline Cu2-xSe with cubic structure.