A series of NiO/SiO2 catalysts with different NiO loadings were first prepared using the impregnation method. The basic characterization of NiO/SiO2 samples was characterized by BET and XRD. The performance of NiO/SiO2 on catalytic decomposition of N2O was evaluated in a fixed bed reactor, which indicated that the best performance on catalytic decomposition of N2O was the sample when the loading of NiO was 16.0 (wt%), NiO(16.0%)/SiO2. On this basis, a series of NiO(16.0%)-Mn2O3(x%)/SiO2 catalysts were prepared, respectively. The experimental results showed that when the loadings of Mn2O3 was 6.0 (wt%), i.e., NiO(16.0%)-Mn2O3(6.0%)/SiO2, its performance on catalytic N2O decomposition was the best. The NiO (16.0%)-Mn2O3(x%)/SiO2 samples were characterized by using XRD and H2-TPR. The stability test in the laboratory fixed bed reactor lasted for 100 hours and showed that the NiO(16.0%)-Mn2O3 (6.0%)/SiO2 catalyst had good stability for the N2O catalytic decomposition, which provided the basis for further relative research.