Multi-channel　transient　electromagnetic　(MTEM)　is　an　artificial　source　electromagnetic　detection　method,　the　transmitter　injects　the　high-power　pseudo-random　binary　sequence　(PRBS)　signals　with　different　coding　frequencies　into　the　earth　to　obtain　the　geological　structure　and　the　mineral　resources.　A　novel　active　softswitching　converter　with　loss-less　snubber　for　MTEM　transmitter　is　presented　in　this　paper.　In　contrast　to　the　conventional　DC/DC　converter,　the　main　switches,　auxiliary　switches　and　rectifier　diodes　of　the　proposed　converter　can　achieve　soft-switching　from　nearly　zero　to　full　load.　According　to　the　change　of　the　load　power,　the　proposed　converter　can　operate　in　the　passive　softswitching　or　the　active　soft-switching.　Under　the　action　of　the　cut-off　diodes　and　auxiliary　windings　coupled　to　the　main　transformer,　the　auxiliary　switches　achieve　softswitching　without　increasing　the　electric　stress　of　the　devices.　In　addition,　the　conduction　loss　and　switching　loss　are　greatly　reduced　than　the　ordinary　auxiliary　circuits.　The　loss-less　snubber　in　the　output　rectifier　is　composed　of　a　controlled　switch,　a　capacitor　and　a　diode,　which　ensures　the　soft-switching　for　the　rectifier　diodes.　So　the　voltage　ringing　across　the　output　rectifier　is　clamped.　The　transmission　efficiency　and　power　density　of　the　proposed　converter　are　significantly　improved　than　the　conventional　converter.　Firstly,　the　topology　of　the　proposed　converter　and　the　timing　diagram　of　control　signals　are　described.　Secondly,　the　working　principle　of　the　converter　is　analyzed　in　detail.　And　then,　the　relationship　between　the　operating　modes　and　the　load　power　is　given.　Finally,　the　Saber　simulation　and　experimental　results　verify　the　feasibility　and　validity　of　the　converter,　and　a　60kW　prototype　is　implemented.　©　2017　IEEE.