High-frequency　large　current　tests　are　critical　in　almost　all　switch-mode　power　conversion　systems.　To　measure　this　large　current,　large　size　current　sensor　with　large　current　rating　is　always　needed　to　bring　many　disadvantages　of　bulk　volume,　less　accuracy　and　high　cost.　One　of　the　solutions　is　to　use　current　split　technique　with　the　split　wires　of　the　winding　in　magnetic　components　to　measure　the　current　in　only　one　of　the　strands　of　the　multi-strands　Litz　wires　in　magnetic　components.　In　this　paper,　the　mechanics　of　the　current　split　ratio　shifts　for　different　frequencies　are　revealed.　The　model　is　also　built　and　analyzed　to　find　that　the　leakage　inductance　ratio　between　the　current　testing　strand　and　other　strands　is　the　key　factor　which　dominates　the　current　split　ratio.　Based　on　the　model,　a　simple　method　was　proposed　to　improve　the　current　split　ratio　for　different　frequencies.　The　practical　tests　were　performed　to　verify　the　method　and　its　current　testing　precision.　©　2012　IEEE.