Abstract: The present invention provides a catalyst for reduction of nitrogen oxides represented by the formula (A.sub.a O.sub.x.B.sub.b O.sub.y).(C.sub.c O.sub.z.C'.sub.c' O.sub.z')/S which is produced by supporting mixed metal oxides represented by the formula (A.sub.z O.sub.x.B.sub.b O.sub.y).(C.sub.c O.sub.z.C'.sub.c' O.sub.z') in amorphous state on aluminum or silicon-containing support at calcination temperature of 400.degree. to 700.degree. C. in a molar ratio of 0.01:1 to 5:1, anda method for removing nitrogen oxides through selective catalytic reduction which comprises converting 50 to 50,000 ppm of nitrogen oxides in exhaust gas from automobile or from fixed source such as plant turbine and boiler, and other industry in a state of having 0.1 to 20% of excessive oxygen over (A.sub.a O.sub.x.B.sub.b O.sub.y).(C.sub.c O.sub.z.C'.sub.c' O.sub.z')/S catalyst by using 100 to 100,000 ppm of hydrocarbon reducing agent having 1 to 5 carbons under the reaction condition of 200.degree. to 800.degree. C.