Cu-In-2Se powders were synthesized by hydrothermal co-reduction method from CuCl2.2H2O, InCl3.4H2O and SeO2 at 95～200 °C in deionized water. The morphology and phases of the products were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) respectively. Experimental results show that, CuInSe2 can be obtained at 120～200 °C, the major phase of the products synthesized at 120～200 °C are all the same. However the noticeable impurity phase In(OH)3 still exists in the product powders. The In(OH)3 phase decreases with the increasing of reacting temperature. The product powder obtained at 200 °C has fine and homogeneous particles with diameters of about 500 nm.