A　technology　for　fabricating　negative　electron　affinity　(NEA)　multi-alkali　photocathodes　is　described.　A　reflection-mode　NEA　multi-alkali　photocathode　of　(Na2KSb-Cs)-O-Cs　structure　with　a　maximum　photosensitivity　of　700　μA/lm　is　fabricated.　The　quantum　yield　of　the　NEA　(Na2KSb-Cs)-O-Cs　photocathode　is　presented.　The　roles　of　cesium　and　oxygen,　the　surface-layer　model,　and　the　energy　diagram　of　the　photocathode　thus　fabricated　are　also　discussed.　©　1993.