Cobalt catalysts for gas mask loaded on various supports such as $Al_{2}O_{3},;TiO_{2}$, AC(activated carbon) and $SiO_{2}$ were used to examine influences of calcination temperatures and reaction temperatures for CO oxidation. $Co(NO_{3})_2{cdot}6H_{2}O$ was used as cobalt precursor and the catalysts were prepared by incipient wetness impregnation. The catalysts were characterized using XRD, TGA/DTA, TEM, $N_{2}$ sorption, and XPS. For the catalytic activity, support was in the order of ${gamma}-Al_{2}O_{3}>TiO_{2}>SiO_{2}>AC;and;Al_{2}O_{3}$. The catalytic activity at lower temperature than $80^{circ}C$ showed that with the increase of reaction temperature, cobalt catalysts on ${gamma}-Al_{2}O_{3},;TiO_{2},;AC$ has the negative activation energy but that of $SiO_{2}$ was positive.