Abstract: Herein.we reported the miniaturization design of the energy transfer coupling structure of X-band mini-traveling wave tubes(TWTs).a core component of microwave power module.for the purpose of efficiency improvement.The original work was the novel design method.in which the energy transmission length was shortened by loading the regulative tube at the end of the helix slow wave structure(SWS).The impedance matching structure was designed and optimized.The properties of the miniaturized coupling structure was mathematically modeled and numerically simulated with software HFSS.The simulated results show that the impedance-transform sizes of the input/output windows were decreased by 33.0% and 21.4%.respectively.and that the total TWT efficiency was improved.We suggest that the newly-developed energy transfer coupling structure be of some technological interest in miniaturization design of mini-TWTs other than X-band.