The　rational　design　of　inexpensive　and　highly　efficient　electrocatalysts　for　ethanol　oxidation　reaction　(EOR)　is　crucial　for　direct　ethanol　fuel　cells.　In　this　study,　a　series　of　carbon　-supported　PtCu　electrocatalysts　with　varying　Pt/Cu　ratios　were　synthesized　using　a　microfluidic　system.　This　system　enabled　the　separation　of　heterogeneous　nucleation　and　nanocrystal　growth　based　on　segmental　thermal　induction.　Heterogeneous　nucleation　occurred　at　the　low　-temperature　zone,　which　resulted　in　uniform　loading,　while　the　enhancement　of　solvent　reducibility　in　the　high　-temperature　region　enabled　the　control　of　the　PtCu　nanoparticle　composition.　The　synthesized　PtCu/C　electrocatalyst,　with　Cu　content　adjustable　from　17%　to　38%,　exhibited　high　crystallinity　and　homogeneous　dispersion,　with　an　average　particle　size　of　3.9　nm.　These　advantageous　physical　properties　endowed　the　PtCu/C　electrocatalysts　with　significantly　enhanced　electrocatalytic　performance　for　EOR　compared　with　commercial　Pt/　C　catalysts.　The　development　of　this　method　presents　a　novel　approach　for　the　controlled　preparation　of　supported　catalysts.