CO combustion catalysts of Au loaded on Co3O4 which contains high concentration of Au (3, 10, 20, and 40 wt%) for the integration on the microdevice were developed and the combustion performance of these catalysts were evaluated. The highly dispersed Au/Co3O4 catalyst was prepared using the mechanical mixing of the Au colloid (average particle size of 3 nm) and a cobalt oxide powder (particle size of 20-30 nm). The catalyst preparation by the colloid process could result a better dispersion of Au particles in the Au/Co3O4 catalyst. The Au particle size of the Au content of 20 wt% was 1/10 of that by the catalyst of same composition prepared by impregnation process in our previous studies. This improvement of microstructure enhanced the combustion performance of the catalyst, which was improved 10 times as compared to that of our previous study. Moreover, the CO selectivity of the Au/Co3O4 catalyst on the microdevice depended on the Au particle size.