The　development　of　electrode　materials　with　high　reversible　capacity,　superior　rate　capability,　and　long　lifespan　for　sodium-ion　and　potassium-ion　batteries　(SIBs/PIBs)　is　gaining　great　attention.　Herein,　V3Se4　nanoparticles　embedded　in　nitrogen/phosphorus　co-doped　carbon　nanofibers　(V3Se4/NPCNFs)　were　initially　synthesized　with　the　assistance　of　biomass　algae　(Chlorella　pyrenoidosa)　and　employed　as　anodes　in　SIBs　and　PIBs　for　the　first　time.　The　experimental　findings　and　DFT　calculation　results　reveal　that　heteroatom　N/P　co-doping　could　increase　the　content　of　pyridinic　N　with　more　open　edge　sites　and　boost　the　Na+/K+　storage　performance　by　optimizing　the　distribution　of　electron　density　and　enhancing　ion　reaction　kinetics.　As　a　result,　the　V3Se4/NPCNFs　electrode　exhibits　an　admirable　capacity　(527　mAh　g-1/0.1　A　g-1/60　cycles)　and　ultralong　cycle　performance　(340　mAh　g-1/5　A　g-1/8000　cycles　and　240　mAh　g-1/10　A　g-1/13000　cycles)　for　SIBs　as　well　as　an　excellent　electrochemical　performance　for　PIBs　(450　mAh　g-1/100　cycles　at　50　mA　g-1　and　207　mAh　g-1/800　cycles　at　2　A　g-1).　The　SIB　full　cell　obtained　by　pairing　with　a　Na3V2(PO4)3　cathode　also　reveals　outstanding　cycling　performance.　Thus,　this　work　helps　explain　how　biomass　algae　is　a　sustainable　and　economical　source　of　heteroatoms　and　reactor　in　constructing　energy　storage　materials.