The alkaline earth metals have recently been reported to exhibit a similar role as alkali metals in enhancing the low temperature formaldehyde (HCHO) oxidation performance of precious metal supported catalysts; however, its essential mechanism is still not well understood. In this work, it is found that the Pt precursor is critical for Ba-mediated Pt/TiO₂ catalyst to achieve the efficient HCHO oxidation performance. Catalytic results indicate that Pt/TiO₂ catalysts using tetraammineplatinum(II) nitrate (Pt(NH₃)₄(NO₃)₂) and chloroplatinic acid (H₂PtCl₆) as Pt precursors exhibit comparable performance in HCHO oxidation. Notably, the Ba-mediated Pt/TiO₂ catalyst synthesized from Pt(NH₃)₄(NO₃)₂ shows exceptional catalytic performance, with its HCHO reaction rate being 3.8-fold that of Pt/TiO₂, while the Ba-mediated Pt/TiO₂ catalyst derived from H₂PtCl₆ has the similar catalytic activity to that of Pt/TiO₂. Series characterization results reveal that the Ba species can strongly interact with Pt to form the Ba-O-Pt active site within the Ba-mediated Pt/TiO₂ catalyst derived from Pt(NH₃)₄(NO₃). However, such interaction is not observed in the catalyst synthesized from H₂PtCl₆. Additionally, more oxygen species and hydroxyl groups can be adsorbed and activated on the Ba-O-Pt active site than those on the typical Pt active site, and HCHO undergoes efficient oxidation on the Ba-O-Pt active site via a different reaction pathway (HCHO→HCOO⁻ + OH→H₂O + CO₂) analogous to that observed on alkali metal-mediated active site. These findings can provide a deep insight into the development of highly efficient catalysts for low temperature HCHO oxidation.