One of the important building blocks on Qiangguang I accelerator is longpulse highimpedance intense electron beam diode, which is mainly used to convert electrical pulse from long pulse power generator into electron beam and intense bremsstrahlung. In this paper, the long pulse power system on Qiangguang I accelerator is introduced. The insulation characteristics of insulator and MITL of longpulse highimpedance intense electron beam diode were analyzed in detail. The design approach for diode operating parameters including the diode impedance, cathode and anode are described. The experimental results are:the diode voltage is 0.75~2.6MV,the beam current is 65~85kA,the impedance corresponding to the amplitude of diode voltage is 14~44Ω,the pulse duration of bremsstrahlung is