Abstract: A 10-stage 200 kV mini-Marx generator based on waveerection principle has been designed in coaxial structure. The capacitors, connecting switches and metallic enclosures, lead to the establishment of a fast pulse forming line. And fast risetime is achieved through the proper design of the stray capacitance and interstage capacitance, in concern with coupling the spark gaps via ultra-violet energy. The generator was demonstrated to deliver pulses of more than 210 kV onto a 70 Ω load with 40 ns pulse width and 6 ns risetime. With a flash X-ray tube integrated directly into the generator as a load, the formed flash X-ray system could generate a dose of 7.7×10－6 C/kg at 25 cm away for flash X-radiography．