An axle-coupled energy switch for standing wave accelerator tub e is composed of step motor, worm-wormwheel speed-varying mechanism, roller-type leading screw, flexible bellows, energy regulating rodand cavity partition. Said cavity partition has central nose cone. Cooling water channel is arranged at its periphery and in its center. The kidney-shaped coupling holes arranged alternatively by 90 degrees in axial direction are positioned on circumference. The energy regulating rod is inserted into the kidner-shaped hole. Said energy switch can serve to regulate the distribution for field intensity in main acceleration segment which ensure the field intensity in focusing segment to be constant.