Abstract: Linear transformer driver (LTD) is a new electrical circuit topology developed in recent years which has a number of significant advantages such as compactness, flexible output parameters and high energy transfer efficiency. According to the requirement for flash X-ray radiography, the pulsed driver which can deliver 3 MV on a 40 rod pinch diode (RPD) has been designed. The machine is composed of 30 square pulse LTD stages in series with a total length of 8 meters. Each LTD stage contains 12 fundamental bricks each consisting of two 10 nF capacitors and a multi-gap switch connected in series and 4 harmonic bricks each consisting of two 1 nF capacitors and a multi-gap switch connected in series. The transformer oil is used as voltage adder insulator. According to the equivalent circuit simulation, the generator can produce more than 3 MV fast pulse in 16.8 ns with 98 ns FWHM.