The rational design of low-cost catalysts with excellent catalytic activity is one of the most significant topics in heterogeneous catalysis. LaFeO3 (LFO) perovskite was synthesized by the citrate sol-gel method and followed through a selective dissolution method by acid solutions. The surface element percentage, chemical states and pore structure of LFO were tuned. The acid-treated catalyst (LFO-H) showed higher activity in CO oxidation than the raw LFO. In terms of various characterizations, the exposed La ions of the LFO were slightly etched by dilute nitric acid, but the LFO-H still preserved the original perovskite framework. The corresponding surface area, surface oxygen vacancies and reducibility were also improved after acid treatment, accounting for its higher catalytic activity. Moreover, the LFO-H also exhibited excellent thermal stability because the perovskite structure remains after acid treatment.