Methane emission and treatment is an extremely important environmental problem, and the key and core treatment method are the application and development of catalysts in the after-treatment system. In this study, a new non-noble metal catalyst, which named OALSM, was fabricated by etching La_0.8Sr_0.2MnO₃ with oxalic acid for the removal of methane. Related experiments and theoretical explorations by scholars had shown that acid etching of perovskite surfaces could achieve effective optimization of the catalytic oxidation properties and microscopic physical and chemical properties of the materials. And the oxalic acid reacted with high-valence state Mn to generate abundant coordination unsaturated Mn³⁺ sites, which could produce more active oxygen species. In addition, OALSM showed a higher methane catalysis capability than the samples that were not subjected to acid etching. Among all the as-prepared catalysts, OALSM-0.01 M demonstrated the optimal methane catalytic activity with the T₅₀ value of 336 °C, the T₉₀ value of 417 °C, the activation energy of 47.02 kJ·mol⁻¹, and the favorable structural stability and toxicity resistance. This integration strategy can rationalize an innovative protocol to into the design of composite catalysts for methane oxidation, to broaden the application of acid etching in VOC oxidation.