Some　multi-principal　element　alloy　(MPEA)　catalysts　may　exhibit　the　ability　to　promote　the　hydrogen　evolution　reaction　(HER)　and　maintain　stability　under　acidic　conditions.　Here,　we　investigated　the　impact　of　ordered　behavior　and　surface　oxidation　of　FCC_CoCrFeNi　and　Co0.35Cr0.15Fe0.2Mo0.1Ni0.2　MPEAs　on　HER　performance　through　first-principles　calculations.　The　ordering　behaviors　of　MPEAs　were　described　using　L12_AuCu3　sublattice　model　and　the　predicted　site　occupying　fractions　(SOFs).　And　we　found　that　the　catalytic　activity　of　single　intermediate　*H　at　top　or　bridge　adsorption　sites　surpassed　that　at　the　hollow　site.　However,　the　hollow　site　exhibits　strong　adsorption　towards　*H,　resulting　in　the　transfer　of　*H　from　other　sites　to　hollow　site.　Meanwhile,　compared　to　those　containing　only　hydrogen,　MPEAs　with　both　hydrogen　and　oxygen　exhibit　lower　overpotentials,　primarily　due　to　oxygen　facilitating　hydrogen　adsorption　and　subsequent　desorption　from　MPEA　surfaces,　thus,　such　fundamental　finding　highlights　the　beneficial　role　of　alloy　surface　oxidation　in　promoting　HER　performance.　Furthermore,　the　overpotential　values　of　the　three　slab　models　based　on　SOFs　are　similar,　demonstrating　considerably　consistent　atomic　distribution　behaviors,　thereby　better　reflecting　the　overall　catalytic　performance　of　ordered　MPEAs.　These　explorations　bring　new　insights　into　the　ordered　behavior　and　surface　oxidation　of　MPEAs　in　HER　catalysis.　©　2024　Elsevier　B.V.