In　the　area　of　water　electrolysis,　molybdenum　sulfide　(MoSx)　materials　have　attracted　a　lot　of　interest　and　investigation　due　to　their　platinum-like　catalytic　activity.　Herein,　this　work　describes　the　synthesis　of　a　novel　molybdenum-based　coordination　metal　polymer　(CMP)　by　adding　s-triazine-2,4,6-trithiol　(C3H3N3S3)　ligands　under　mild　conditions,　which　addresses　the　issues　of　poor　electrical　conductivity　and　limited　exposure　of　active　sites　in　conventional　MoSx　materials.　Combination　of　X-ray　absorption　near-edge　spectroscopy,　X-ray　photoelectron　spectroscopy,　and　in　situ　Raman　spectroscopy　identifies　the　key　role　of　N,　S　co-coordinated　Mo　defect　site　[MoV(O)SxNy]　moieties　as　active　sites　in　alkaline　hydrogen　evolution　reaction　(HER)　processes.　Benefitting　from　the　good　electrical　conductivity　of　the　CMP　network,　the　efficient　dispersion,　and　anchoring　of　the　oxygenated　molybdenum　sites　by　N　and　S,　the　optimized　Mo-based　CMP　exhibits　a　high-efficiency　alkaline　HER　(η10:　87　mV)　with　30,000　CV　times　cycle　stability.　This　good　HER　catalyst　also　shows　well　durability　at　100　mA　cm-2　for　80　h　in　alkaline　simulated　seawater　(1　M　KOH　+　0.5　M　NaCl).　This　work　inspires　new　ideas　to　design　N,　S　co-coordinated　molybdenum-based　CMP　electrocatalysts　for　hydrogen　production　by　commercial　alkaline　water　splitting.　©　2023　American　Chemical　Society.