In this research, CuO powder was prepared by low temperature hydrothermal method. Copper (II) nitrate trihydrate (Cu (NO 3 ) 2 .3H 2 O) and sodium hydroxide (NaOH) were used as the starting precursors. The final pH value of the mixed solution was adjusted to 9 by 4M NaOH and treated at 100 oC and 200 oC for 4 and 6 h. The black fine powder was obtained after dried at 80 oC for 4 h. The phase was characterized by X-ray diffraction (XRD). A single phase of monoclinic structure of CuO powder prepared by low temperature hydrothermal method at 200 oC for 4 and 6 h was obtained without calcination step. The morphology and particle size were investigated by scanning electron microscopy (SEM). The morphology was flower-like in shape and the average particle size in range of 0.3×0.7 μm. The element composition was indicated by energy dispersive X-ray spectrometry (EDX). The chemical compositions showed the characteristic X-ray energy of copper (Kα = 0.95 keV) and oxygen (Kα = 0.53 keV). The functional group was indentified by fourier transform spectrophotometry (FTIR). The wavenumber at 433-531 cm - 1 was corresponded to vibration of Cu-O stretching.