The invention discloses a converter transformer and a conversion system, relates to the high voltage DC power transmission technical field, and aims to solve the problems that an existing conversion system cannot support more pulse numbers; the converter transformer comprises a three-phase current input end and four transformation units; the three-phase current input end is respectively connected with input ends of the four transformation units; the output ends of the four transformation units are used for outputting four voltages with same output amplitude, and phase positions differ by 15 degrees in sequence. The converter transformer and conversion system can be applied to high voltage DC power transmission conversion.