gamma-MnO2, SmMnO3, and gamma-MnO2/SmMnO3 catalysts were prepared by facile methods, wherein the SmMnO3 (SMO) perovskite was synthesized through one-step calcination and the gamma-MnO2/SmMnO3 was formed by an in situ growth of gamma-MnO2 on the surface of SMO. These materials ware characterized by XRD, SEM-mapping, N-2-adsorption, XPS and H-2-TPR to investigate their textural properties. Compared with that of SMO and gamma-MnO2, the gamma-MnO2/SMO shows better performance for catalytic oxidation of aromatic VOCs in wet air (10 vol.%), which may be attributed to its higher surface molar ratio of lattice oxygen to adsorbed oxygen (O-latt/O-ads) and better low-temperature reducibility. Besides, for gamma-MnO2/SMO catalyst, a successive oxidation route and the inner principle of BETX (benzene, ethylbenzene, toluene, and o-xylene) oxidation were also revealed via various tests and a comprehension of dynamics investigation. Meanwhile, the experiments under simulated realistic exhaust conditions displayed that the gamma-MnO2/SmMnO3 is also a good catalyst with high stability for aromatic VOCs oxidation, and fulfilled endurability to high humidity (20 vol.%).