Zinc oxide (ZnO), a wide bandgap (3.4 eV) Ⅱ-Ⅵ compound semiconductor, has a stable wurtzite structure with lattice spacing a= 0.325 nm and c= 0.521 nm. Zinc oxide powders were synthesized by a simple hydrothermal process in the different reaction pH, temperatures, and precursor concentrations. Nanoparticles were formed by simple hydrothermal synthesis of mixing aqueous solutions of zinc nitrate hexahydrate (Zn(NO3)2· 6H2O) and NaOH under controlled process conditions such as precursor reaction pH, concentration and temperatures. And zinc oxide seed layer was coated by Metal-Organic Decomposition (MOD) process, and then the zinc oxide nanorods on ZnO seed layer were grown by hydrothermal process from 0.3 M at pH 7, 80 ℃, 1 h. Single phase zinc oxide particles can be easily synthesized in lower precursor concentration, higher reaction pH and temperature. Zinc oxide mophology of shorted hexagonal tablet crystals, multipods, interconnected or separate rods, could be obtained and the shapes would be efficiently controllable by changing hydrothermal conditions. ZnO nanorods can be easily formed on the ZnO coated glass substrate in low temperature using ZnCl2.