The　extended　synthetic　vector　method　was　applied　to　derive　an　easy-solved　mathematic　model　to　study　the　bar　current　distribution　on　a　multi-broken-rotor-bar　squirrel-cage　induction　motor.　Mathematical　simulations　performed　on　both　transient　and　steady　states　revealed　the　bar　current　distribution＇s　feature,　and　a　close　relationship　between　the　maximum-bar-current　and　parameter　setting　like　broken-bar　quantity,　broken-bar　relative　position.　Simulations　results　indicated　that　the　cycle　of　bar　current　versus　space　is　in　one　pair-pole.　The　bar　with　maximum　current　is　positioned　either　adjacent　to　the　broken-bar　or　is　in　one　pair-pole　space.　The　maximum　bar　current　changes　with　the　broken　bar　position　on　a　multi-broken-bar　case.　For　a　given　bar　quantity,　the　value　for　maximum　bar　current　reaches　maximum　when　the　broken-bar＇s　relative　position　is　in　one　pair-pole　space.　All　bar　current　values　are　equal　if　specially　positioned　broken-bars.　The　study　results　are　directly　applicable　to　induction　motors　on-line　diagnosis　and　troubleshooting.