For　improving　the　preciseness　of　protection　action　and　reliability　of　electric　equipment,　according　to　process　and　technology　of　protection　setting　calculation.　This　paper　presents　a　module-based　setting　calculation　system　of　relay　protection　for　power　plant.　The　structure,　function　and　design　method　of　system　are　proposed.　OOP　and　visual　technology　are　used　in　software　design.　System　is　composed　of　graphic　modeling,　fault　current　calculation,　setting　calculation　of　relay　protection　and　data　management.　It　is　easy　to　take　account　of　expert　acknowledge　during　the　calculation　and　management　to　optimize　the　setting　calculation.　It　will　release　people　from　the　complex　setting　calculation.　Result　of　setting　calculation　is　believable.