A　study　on　the　effect　of　MnZn　Ferrite/FeSiAl　powder　composite　core　materials　on　the　suppression　property　of　high　frequency　EMI　was　carried　out.　The　suppression　mechanism　of　high　frequency　EMI　of　the　composite　materials　was　analyzed　and　the　course　how　to　prepare　the　core　was　designed　and　introduced.　The　key　processes　of　FeSiAl　was　analyzed　and　the　magnetic　loss　characters　of　cores　were　compared　and　analyzed.　The　experimental　results　show　that　the　core　made　of　external　oxidation　powder　is　obviously　improved　in　EMI　suppression　performance,　the　average　value　of　μ″　is　9.98　in　the　frequent　range　between　1GHz　and　1.8GHz　and　the　maximum　value　is　13.33,　In　addition,　the　performance　of　composite　cores　made　by　bonding　in　high-frequency　EMI　suppression　is　better　(the　average　value　of　μ″　is　8.64).　Instead　composite　cores　prepared　by　sintering　degrade　in　EMI　suppression　performance　because　internal　oxidation　reaction　is　not　easy　to　control.