In this work, MnO2/LaMnO3 catalysts derived from LaMnO3 perovskite were prepared in situ via a facile selective removal and oxidation method using acidic KMnO4 solution. For bulk LaMnO3 perovskite, the A-site cations (La) were dissolved and B-site cations (Mn3+) were simultaneously oxidized to Mn4+ with acid treatment. The modified catalyst exhibited better activity for toluene oxidation than bulk LaMnO3. This method improves the Mn4+ content on the LaMnO3 surface with good low temperature reducibility. Meanwhile, this method increases the specific surface area and provides more oxygen vacancies on the surface. These results are beneficial for the toluene adsorption and its ring-opening reaction. Moreover, MnO2/LaMnO3 still maintained good thermal stability for toluene oxidation at high temperatures resulting from the presence of the perovskite structure.