Cobalt oxide nanoparticles (Co3O4) were synthesized by wet chemical method using cobalt sulfate as precursor and ethylene glycol as surfactant. Their physico-chemical properties were characterized by high resolution transmission electron microscopy (HRTEM), field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) and vibration sampling magnetometer (VSM) analyses. The crystal structure of samples after annealing was done by XRD analysis. XRD measurement exhibited the structure of Co3O4 nanocrystals for annealed samples. The TEM results showed the cobalt oxide nanoparticles with good uniformity. The SEM images revealed that the size of nanoparicles increased in the range of 20-50 nm with increasing annealing temperature. The magnetic results indicated a good coercive field and saturation magnetism around 452 G and 18 emu/g, respectively.  
