The V-K catalysts were produced on porousα-alumina substrate by a solution im-pregnation route and the compositions and catalytic activities for soot oxidation were studied by XRD, TG/DTG,DSC and TPR.According to the catalytic activity studies,the catalytic activity of the crys-talline phases is in the order:KNO_3+KVO_3＞K_3V_5O_(14)+KVO_3.The appearance of excessive KHCO_3 phase will lead to the deterioration of catalytic activity when the catalysts contain higher KNO_3 content. strong CO_2 absorption characteristic and this behavior will become gradually significant with the in-lattice with onset desorption temperature of 200℃.