Pt‐based intermetallics are regarded as highly efficient electrocatalysts for oxygen reduction reaction (ORR). However, Pt‐based intermetallics with different Pt: M atomic ratios have different atomic arrangements and crystal structures, which will change the electronic structure and coordination environment of Pt, thus affecting the electrocatalytic activity. In this work, we prepared L12‐Pt3Co and L10‐PtCo intermetallic catalysts by modulating the molar ratio of Pt and Co precursors using a thermal annealing method. The mass activity (MA) of L10‐PtCo is 0.52 A mg‐1Pt at 0.9 V, which is 1.44 times larger than that of L12‐Pt3Co (0.36 A mg‐1Pt). In addition, the MA of L10‐PtCo decreases by 17.31 % after 10,000 CV cycles, which is smaller than that of L12‐Pt3Co (25.00 % loss in MA), showing excellent structural stability. Theoretical calculations reveal that compared to L12‐Pt3Co, L10‐PtCo has more electrons transferred to the Pt sites, which further optimizes the electronic structure of Pt and reduces the d‐band center, leading to the increase of the electrocatalytic performance. This work provides new insights into the study of Pt‐based intermetallics with different Pt: M ratios, which is helpful for the screening and preparation of high‐performance Pt‐based intermetallics.