Potassium promoted Co-Mo catalysts supported on flash-calcined alumina for sour WGS process have been prepared. The oxide form of samples has been characterized by ICP-OES method, adsorption, temperature-programmed reduction (TPR) and the sulfides form after the catalytic activity test by means of XPS. Catalytic activity measurements were carried out in gradientless reactor in a kinetic region at low partial pressure of reagents. A strong effect of the promoter addition sequence to the support has been observed. The highest activity in the WGS process was determined for the potassium promoted catalyst with a K/Mo ratio of 0.06 obtained by a simultaneous impregnation of flash-calcined alumina with aqueous solution of K and Mo salts. Potassium addition significantly changes reducibility and decreases total surface area of catalysts. XPS results show that the catalyst activity is correlated with the surface concentration of and Co-Mo-S species. Potassium addition enhances the formation of such species. The method of potassium incorporation to the catalyst has been suggested and its optimal content has been determined. The catalyst obtained can be implemented in industrial processes of hydrogen and syngas production from feedstocks with high sulfur content.