The　development　of　efficient　and　economical　nonprecious　metal　electrocatalysts　is　crucial　for　advancing　the　industrialization　of　the　hydrogen　evolution　reaction　(HER)　in　water　electrolysis.　WS2　has　become　a　hotspot　in　HER　research　due　to　its　unique　physicochemical　properties　and　potential　applications.　In　this　work,　a　series　of　Mo-WS2-n　(n　=　0,　0.3,　0.5　and　1.0,　representing　H2　pressure)　samples　with　abundant　sulfur　vacancies　were　prepared　by　utilizing　H2　as　the　structure　directing　agent　(SDA).　Among　them,　the　Mo-WS2-0.5　sample　possessing　abundant　sulfur　vacancies　demonstrated　best　acidic　HER　performance　by　displaying　an　overpotential　of　146　mV　at　10　mA　cm-2　and　the　Tafel　slope　of　46.8　mV　dec-1,　which　is　superior　to　most　reported　WS2-based　electrocatalysts.　Furthermore,　Mo-WS2-0.5　exhibits　good　stability,　proving　its　potential　in　practical　applications.　During　the　synthesis　process,　H2　can　effectively　remove　S　atoms　from　WS2　to　create　sulfur　vacancies.　Theoretical　calculations　unravel　that　both　Mo　doping　and　sulfur　vacancies　can　significantly　reduce　the　Gibbs　free　energy　of　hydrogen　atom　adsorption　(Delta　G　H)　of　WS2.　This　study　not　only　offers　new　insights　into　understanding　the　effects　of　metal　doping　and　sulfur　vacancies　in　WS2　on　acidic　HER,　but　also　provides　a　practical　approach　for　designing　low-cost　and　high-performance　non-noble　metal　electrocatalysts.