Alloy　catalyst　is　considered　to　be　an　important　strategy　to　solve　the　shuttle　effect　and　sluggish　kinetics　of　lithium-sulfur　batteries　(LSBs).　However,　the　effect　of　the　electronic　structure　of　the　alloy　catalyst　on　the　sulfur　conversion　process　has　not　been　effectively　analyzed.　In　this　paper,　based　on　alloying　strategy,　the　electronic　structure　of　such　a　FeCoNi　catalyst　is　regulated　and　optimized,　and　the　sulfur　adsorption　configuration　and　catalytic　conversion　process　are　defined.　The　in　situ　Raman　spectroscopy　and　the　density　functional　theory　(DFT)　are　employed　to　deeply　understand　the　catalytic　mechanism　of　such　a　sulfur　conversion.　A　cell　with　FeCoNi　modified　separator　delivers　an　ultra-low　capacity　attenuation　of　0.056%　per　cycle　over　1000　cycles　at　3　C.　The　outstanding　anti-self-discharge　performance　of　8.1%　over　7　days　is　also　achieved.　Furthermore,　the　obtained　cell　with　a　high　sulfur　loading　of　9.7　mg　cm-2　and　lean　electrolyte　of　5.6　mu　L　mgs-1　exhibits　81%　capacity　retention　after　100　cycles,　providing　a　research　prospect　for　the　practical　application　of　lithium-sulfur　batteries.　Based　on　the　intrinsic　electronic　structure　of　the　alloy　catalyst,　the　surface　electronic　reconstruction　process　of　the　alloy　catalyst　is　analyzed,　and　its　catalytic　mechanism　in　the　sulfur　conversion　process　is　elucidated,　which　provides　a　new　idea　for　the　development　of　alloy　catalyst　and　lithium　sulfur　battery.　image