In this paper, the methods of spin polarization density functional theory and vasp software package are used to simulate the adsorption of H2O molecules on the surface of LaCoO3 and La2CoFeO6(001). It was found that when Fe was doped at B-sites, the adsorption energy changed from -3.7493 eV at CoO2 to -2.5397 eV at CoFeO4, which decreased by about 1/3. Meanwhile, the change of electric charge and the amount of electron transfer decreased overall. The results indicated that Fe doping could inhibit the adsorption of H2O by perovskites and thus hinder the next toxic reaction. Therefore, this paper will lay a certain theoretical foundation for the study of perovskite anti-poisoning mechanism and provide a meaningful reference for further experimental research.