In the present invention, there is disclosed a catalyst for removing Ni2O from waste gases containing in addition to Ni2O steam, NOix and oxygen through degradation thereof to components that are environment friendly, nitrogen and oxygen, wherein the catalyst comprises calcined cobalt(II) beta-hydroxide impregnated by aqueous solutions of cesium compounds being represented by nitrates or carbonates and cesium concentration is in the range of 0.2 to 3 percent by weight, based on the catalyst total weight. Process for preparing the above-described catalyst is characterized in that cobalt(II) nitrate is brought into reaction with sodium hydroxide in molar ratio NaOH/Co(NOi3)i2 = 0.5 to 2.0 at a temperature ranging from 15 to 30 degC under perpetual agitation for a period of 5 to 10 minutes to obtain a crystalline structure of cobalt(II) beta-hydroxide, which is then dried and calcined at a temperature ranging from 350 to 650 degC for a period of 2 to 8 hours and subsequently it is impregnated by aqueous solution of cesium compounds such as to achieve molar ratio of Cs to Coi3Oi4 concentration within the limits of 0.003 to 0.060 and then is again subjected to calcining at a temperature ranging from 350 to 650 degC for a period of 2 to 8 hours. The thus obtained catalyst decomposes Ni2O from waste gases at a temperature of 350 degC and higher. The concentration of Ni2O in the resulting gas is less than 15 to 10e-3 mole percent, at concentration of Ni2O at the inlet of 0.1 mole percent, and a load of 0.001-gicatal min mle-1.