Marine　controlled-source　electromagnetic　transmitters　(MCSETs)　are　important　in　marine　electromagnetic　exploration　systems.　They　play　a　crucial　role　in　the　exploration　of　solid　mineral　resources,　marine　oil,　and　gas　and　in　marine　engineering　evaluation.　A　DC-DC　controlled-source　circuit　is　typically　used　in　traditional　MCSETs,　but　using　this　circuit　in　MCSETs　causes　several　problems,　such　as　large　voltage　ringing　of　the　high-frequency　diode,　heating　of　the　insulated-gate　bipolar　transistor　(　IGBT)　module,　high　temperature　of　the　high-frequency　transformer,　loss　of　the　duty　cycle,　and　low　transmission　efficiency　of　the　controlled-source　circuit.　This　paper　presents　a　clamping-diode　circuit　for　MCSET　(CDC-MCSET).　Clamping　diodes　are　added　to　the　controlled-source　circuit　to　reduce　the　loss　of　the　duty　ratio　and　the　voltage　peak　of　the　high-frequency　diode.　The　temperature　of　the　high-frequency　diode,　IGBT　module,　and　transformer　is　decreased,　and　the　service　life　of　these　devices　is　prolonged.　The　power　transmission　efficiency　of　the　controlled-source　circuit　is　also　improved.　Saber　simulation　and　a　20　KW　MCSET　are　used　to　verify　the　correctness　and　effectiveness　of　the　proposed　CDC-MCSET.