Nowadays, it is still challenging to prepare highly active O-3 decomposition catalyst, especially with high water resistance used in harsh environments such as high relative humidity (RH). Herein, perovskite LaFeO3 based catalysts are synthesized by a facile sol-gel method, which show far higher O-3 decomposition activity of 70-80% than the commonly used Fe2O3 counterpart of 0% at RH 90% and room temperature. Furthermore, 5% mol Ni is effectively doped into LaFeO3 substituting part of Fe as verified by X-ray diffraction and X-ray photoelectron spectroscopy, which enhances the RH resistance with a stable > 90% conversion efficiency on 1000 ppm O-3 at RH 90% and room temperature in a test period of 4.0 h. The temperature programmed desorption results show that the H2O desorption temperature decreases from 180 to 480 degrees C of Fe2O3 to < 100 degrees C for LaFeO3 and LaFe0.95Ni0.05O3, which contributes to the easy desorption of H2O and thus high RH resistance of these perovskite materials. Importantly, the in-situ Raman spectra show deformation of Fe2O3 in O-3 decomposition reaction at high RH, leading to accumulation of intermediate O-2(2-) and thus depression of catalytic activity. However, the perovskite materials show neither deformation nor O-2(2-) accumulation, corresponding well with the high activity at high RH. All these results show the potential of these highly active and RH resistive perovskite catalysts for decomposition of ozone under harsh environments.