The catalyst with an ionic liquid layer (fct-PtCo/C@ILs) is prepared by modifying the chemically ordered platinum-cobalt catalyst (fct-PtCo/C) using hydrophobic ionic liquid 1-butyl-3-methyl imidazolium bis [(trifluoromethyl) sulfonyl] imide ([BMIM] [TFSI]) with high oxygen solubility. According to TEM, FTIR, XPS and TGA measurements, it is confirmed that the ionic liquid has modified the surface of chemically ordered PtCo/C catalyst. The results reveal that the mass activity and specific activity of fct-PtCo/C@ILs catalyst (ILs loading of 5 wt%) reaches 1.04 A mgPt−1 and 1.4 mA cmPt−2, respectively, which are about 8.7 and 7 times higher than that of the commercial Pt/C catalyst. Compared with the catalysts without ILs modification, fct-PtCo/C@ILs shows significantly enhanced electrochemical durability and a higher power density. The addition of ionic liquid can reduce the generation of oxygenated species and promote the release of catalytic active sites. Subsequently, the conductive layer of ionic liquid is formed on the catalyst surfaces, inhibiting the dissolution of metal nanoparticles and the corrosion of carbon supports in acidic electrolytes through physical protection.