Abstract: There are formidable difficulties to generate intense pulsed hard X-ray. The lack of high fidelity high fluence X-ray source has become a restriction factor of SGEMP effect research. The method for intense large-area pulsed hard X- ray production by using a series diode and the radiation parameters are presented in this paper. Flash II accelerator was refined to generate a fast rise time voltage pulse, and a two-stage series diode was developed for coupling electrical energy of high-voltage generator to a low endpoint voltage bremsstrahlung diode via two diodes in series. The X-rays generated by each diode added in space to improve intensity. A dynamic support system was invented to solve the insulation problem of the floating electrode and double-ring cathodes were designed to improve emission uniformity. The experimental results show that the two-stage series diode can work stably under ～700 kV voltage and ～310 kA current, the average energy of X rays is 87 keV, and the fluence is about 36 mJ/cm² over 500 cm² area with dose uniformity 2∶1 at 5 cm from the last converter.