The　nitrogen　cycle　plays　an　important　role　in　nature,　but　N-containing　products　cannot　meet　human　needs.　The　electrochemical　synthesis　of　ammonia　under　ambient　conditions　has　attracted　the　interest　of　many　researchers　because　it　provides　a　clean　and　pollution-free　synthesis　method;　however,　it　has　certain　difficulties,　including　a　high　activation　energy,　multiple　electron　transfer,　and　hydrogenation.　Thermodynamic　factors　limit　the　selectivity　and　activity　of　ammonia　synthesis　techniques.　This　review　summarizes　progress　in　the　electrochemical　synthesis　of　ammonia　from　theory　and　experiment.　Theoretically,　the　reduction　of　nitrogen　molecules　is　analyzed　using　orbit　theory　and　the　thermodynamic　reaction　pathways.　Experimentally,　we　first　discuss　the　effect　of　the　experimental　setup　on　the　nitrogen　reduction　reaction,　and　then　the　four　critical　of　catalysts,　including　size,　electronic,　coordination,　and　orientation　effects.　These　issues　must　be　considered　to　produce　highly-efficient　catalysts　for　electrochemical　nitrogen　reduction　(eNRR).　This　review　provides　an　overview　of　the　eNRR　to　enable　future　researchers　to　design　rational　catalysts.　©　2021　Science　Press