Abstract In this paper, two kinds of preparation methods were used to synthesize CdO nanoparticles. NaOH and citric acid were severally mixed with cadmium nitrate to produce the nanocatalyst via precipitation and sol-gel auto-combustion method respectively. The reactants were either ultrasonicated or mechanically shear-mixed for comparison. And the synthesised samples were characterized for their size and structure using X-Ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. And some molecular groups containing in the nanoparticle were detected by Fourier transformer Infra Red (FT-IR).The result revealed that the catalyst prepared by precipitation method under ultrasonic irradiation possesses the better surface characteristics and optical property, which means that theoretically it will shows great photocatalytic properties in the chemical reaction.