The　reason　why　the　measurement　precision　of　the　aeromagnetic　data　cannot　be　as　high　as　that　of　the　aeromagnetic　instruments　is　due　to　the　level　of　magnetic　interference　of　an　unmanned　aerial　vehicle.　Through　the　analysis　of　electromagnetic　interference　sources　of　unmanned　aerial　vehicles　and　the　working　characteristics　of　optical　pumping　magnetometers,　this　article　intends　to　optimize　the　switch　mode　power　supply　circuit.　Ripple　coefficient　of　output　voltage　is　reduced　to　0.2%,　the　magnitude　spectrum　of　the　near-field　radiation　is　decreased　by　10dB　and　the　conduction　emission　is　below　20dB.　The　electromagnetic　compatibility　of　unmanned　aerial　vehicle　equipment　and　the　measurement　precision　of　the　optical　pumping　magnetometers　are　greatly　improved.