Pt-based　magnetic　nanocatalysts　are　one　of　the　most　suitable　candidates　for　electrocatalytic　materials　due　to　their　high　electrochemistry　activity　and　retrievability.　Unfortunately,　the　inferior　durability　prevents　them　from　being　scaled-up,　limiting　their　commercial　applications.　Herein,　an　antiferromagnetic　element　Mn　was　introduced　into　PtCo　nanostructured　alloy　to　synthesize　uniform　Mn-PtCo　truncated　octahedral　nanoparticles　(TONPs)　by　one-pot　method.　Our　results　show　that　Mn　can　tune　the　blocking　temperature　of　Mn-PtCo　TONPs　due　to　its　antiferromagnetism.　At　low　temperatures,　Mn-PtCo　TONPs　are　ferromagnetic,　and　the　coercivity　increases　gradually　with　increasing　Mn　contents.　At　room　temperature,　the　Mn-PtCo　TONPs　display　superparamagnetic　behavior,　which　is　greatly　helpful　for　industrial　recycling.　Mn　doping　can　not　only　modify　the　electronic　structure　of　PtCo　TONPs　but　also　enhance　electrocatalytic　performance　for　methanol　oxidation　reaction.　The　maximum　specific　activity　of　Mn-PtCo-3　reaches　8.1　A　center　dot　m(-2),　3.6　times　of　commercial　Pt/C　(2.2　A　center　dot　m(-2))　and　1.4　times　of　PtCo　TONPs　(5.6　A　center　dot　m(-2)),　respectively.　The　mass　activity　decreases　by　only　30%　after　2,000　cycles,　while　it　is　45%　and　99%　(nearly　inactive)　for　PtCo　TONPs　and　commercial　Pt/C　catalysts,　respectively.