The　construction　of　hydrogen　evolution　reaction　(HER)　catalysts　at　high　current　density　(HCD)　is　challenging.　Electron/mass　transfer　is　hindered　by　the　unsatisfied　electrical　conductivity　at　the　catalyst-support　interface　and　the　massive　gas　bubbles　adhered　at　the　electrolyte-catalyst　interface　at　HCD　condition.　Herein,　a　non-precious　Ni2P@Cu3P　heterostructure　constructed　by　in-situ　phase　conversion　is　developed　as　an　electrochemical　HER　catalyst.　The　Ni(OH)2　decorated　Cu(OH)2　nanowire　heterostructure　is　completely　converted　into　the　high　electrical　conductive　Ni2P@Cu3P　by　a　simple　phosphatizing　method,　which　not　only　remain　the　3D　nanowire　array　structure　but　also　provide　the　large　specific　active　surface　area　and　plentiful　channels　for　the　fast　charge/　mass　transport　to　accelerate　the　HER　dynamics.　Furthermore,　density　functional　theory　calculations　reveal　that　the　strong　electron　interaction　between　the　Ni2P　and　Cu3P,　which　can　regulate　the　charge　density　distribution.　As-prepared　Ni2P@Cu3P　heterostructure　displays　a　more　moderate　free　energy　(&　UDelta;GH2O　=　-0.37　eV　and　&　UDelta;GH*　=　-0.01　eV)　for　alkaline　HER.　Benefiting　from　the　complementary　advantage　of　Ni2P　and　Cu3P,　the　Ni2P@Cu3P　heterostructure　exhibits　an　enhanced　HER　activity　with　an　overpotential　of　279　mV,　an　excellent　long-term　stability　and　durability　at　1000　mA　&　BULL;cm-　2,　providing　the　great　potential　for　large-scale　industrial　applications.