A repetitive frequency fast pulse hard X-ray generator, diode of the invention is constructed by fixed supporting tubular and sliding supporting tubular, they are connected tightly by the bellows, and grooved rail is set on the bell socket part, rotating otter cylinder is set at the outer to drive the sliding supporting tubular move along the grooved rail; cathode connecting bar is set at the axis in cavity, the front end is cathode target; conical packing ring is set in the cavity of diode to divide the cavity into fore vacuum chamber and back oil recess; anode assembly are fixed at the fore and outer end of the diode. The invention designs the diode to be an active structure, that resolves the technique puzzle of stability of power source, vacuum tightness of diode, axiality of dynamic and static supporting, flexible adjustment on-line; on the precondition of not destroying the vacuum, adjusting aspect ratio flexibly can be realized, the current detecting detector is built; it possesses advantages of flexible structure, repeatable frequency or running for one time, and the pulse width, intensity and power spectrum can be adjustable continuously, it compensates for defects of current technique, and it provides ideal field of radiation for development and application of new type rapid response detector, building fast pulse hard X-ray metering standard, physical mechanism research of diode and pulse ray dynamic imaging technique.