The　exploitation　of　durable　and　highly　active　Pt-based　electrocatalysts　for　the　oxygen　reduction　reaction(ORR)is　essential　for　the　commercialization　of　proton　exchange　membrane　fuel　cells(PEMFCs).Herein,we　designed　Pt@Pt3Ti　core-shell　nanoparticles　with　atomic-controllable　shells　through　precise　thermal　diffusing　Ti　into　Pt　nanoparticles　for　effective　and　durable　ORR.Combining　theoretical　and　experiment　analysis,we　found　that　the　lattice　strain　of　Pt3Ti　shells　can　be　tailored　by　precisely　controlling　the　thick-ness　of　Pt3Ti　shell　in　atomic-scale　on　account　of　the　lattice　constant　difference　between　Pt　and　Pt3Ti　to　optimize　adsorption　properties　of　Pt3Ti　for　ORR　intermediates,thus　enhancing　its　performance.The　Pt@Pt3Ti　catalyst　with　one-atomic　Pt3Ti　shell(Pt@1L-Pt3Ti/TiO2-C)demonstrates　excellent　performance　with　mass　activity　of　592　mA　mgpt-1　and　durability　nearly　19.5-fold　that　of　commercial　Pt/C　with　neg-ligible　decay(2％)after　30,000　potential　cycles(0.6-1.0　V　vs.RHE).Notably,at　higher　potential　cycles(1.0　V-1.5　V　vs.RHE),Pt@1L-Pt3Ti/TiO2-C　also　showed　far　superior　durability　than　Pt/C(9.6％decayed　while　54.8％for　commercial　Pt/C).This　excellent　stability　is　derived　from　the　intrinsic　stability　of　Pt3Ti　alloy　and　the　confinement　effect　of　TiO2-C.The　catalyst＇s　enhancement　was　further　confirmed　in　PEMFC　configuration.