High　power　marine　controlled　source　electromagnetic　transmitters　have　gained　interest　with　applications　in　marine　geological　survey　and　mineral　resources　exploration.　The　direct　current　to　direct　current　(DC-DC)　converter　that　is　typically　used　in　marine　transmitters　has　some　issues,　as　the　insulated-gate　bipolar　transistor　(IGBT)　tube　cannot　achieve　zero-voltage　switching　(ZVS).　In　particular,　lagging-leg　switching　cannot　easily　achieve　ZVS.　The　conversion　efficiency　of　the　heat　converter　requires　improvement.　This　paper　proposes　an　improved　current-doubler　rectifier　for　the　marine　controlled　source　electromagnetic　transmitter　(ICDR-MCSET).　Resonant　inductance　is　increased　and　a　blocking　capacitor　is　added　to　the　converter　(DC-DC)　circuit,　where　the　converter　can　achieve　ZVS　in　a　wide　load　range.　This　results　in　the　effective　decrease　of　the　heating　temperature　and　the　improvement　of　transformation　efficiency.　Saber　software　simulation　and　a　20KW　electromagnetic　transmitter　are　used　to　verify　the　results,　which　show　that　the　method　is　feasible　and　effective.