Recently,　unmanned　aerial　vehicles　(UAVs)　have　become　one　of　the　latest　application　technologies　in　the　aeromagnetic　field.　Furthermore,　high-precision　aeromagnetic　gradient　surveys　need　higher　precision　magnetometers,　and　higher　dynamic　measurement　precision　of　UAVs.　The　problem　of　magnetic　interference　of　UAVs　must　be　solved　to　implement　high-precision　aeromagnetic　surveys,　as　the　switch　mode　power　supply　(SMPS)　is　one　of　the　most　important　interference　sources　of　UAVs.　Through　the　analysis　of　electromagnetic　interference　(EMI)　sources　of　UAVs　and　the　working　characteristics　of　optical　pumping　magnetometers,　this　paper　intends　to　design　and　optimize　the　switching　power　supply　circuit,　reduce　the　generation　of　EMI,　and　improve　the　measurement　precision　of　optical　pumping　magnetometers.　©　2013　IEEE　Electromagnetic　Compatibility　Magazine.