Cobalt oxide(Co3O4) with different morphologies was achieved by a simple solution-based method. Various parallel experiments show that several experimental parameters, such as the concentrations of NaOH and ethylene glycol(EG), play important roles in the morphological controlling of Co3O4 nanoparticles. A lower concentration of NaOH favors quasi-spherical product with a uniform size of about 15 nm, whereas a higher concentration of NaOH generally leads to the formation of nanoplates with wide size distribution. In addition, Co3O4 nanorods were also obtained partially by introducing a certain amount of EG. A possible mechanism was proposed for the selective formation of Co3O4 with various morphologies. X-Ray diffraction(XRD), infrared(IR) spectrometry, scanning electron microscopy(SEM), transmission electron microscopy(TEM) and UV-Vis spectrometry were used to characterize the samples.