Various surface area (SBET) of cobaltic oxide (Co3O4) are prepared by different methods, i.e., precipitation - oxidation, impregnation and hydrothermal. The effect of S-BET of Co3O4 on the catalytic property toward CO oxidation is investigated. The results indicate that the optimum SBET of Co3O4 could increase the catalytic activity. Characterization of the cobaltic oxide using X-ray diffraction (XRD), N-2-adsorption at -196 degrees C, infrared ( IR) and temperature-programmed reduction (TPR) reveals that the increase of SBET on Co3O4 can weaken the bond strength of Co - O and promote more lattice oxygen desorption from Co3O4 to cause the reduction become easy. We conclude that the S-BET effect, caused by various prepared methods and refined conditions, are responsible for the activity enhancement of Co3O4. The T-50 (the conversion of CO reached 50%) is decreased significantly when the SBET is increased, i.e., PO- R230 > PO- C400 > I-C550 > H- 150 similar to D-Strem.