In order to study the biomedical effects in the treatment of tumors exposed to high pulse repetition frequency (PRF) nanosecond pulsed electric fields, a compact pulse generator which can provide high PRF ns pulses is needed. A new configuration of pulse generator combining Blumlein line and transmission line transformer (TLT) is proposed in this paper. The modular generator can provide high PRF ns rectangular pulses whose amplitude and PRF are adjustable with less switches. In this paper, the pulse forming processes of singlestage and multistage generator in matching impedance are theoretically analyzed. The changes of waveforms of multistage generator in mismatched loads are analyzed. Microstrip line is used to design the Blumlein in the generator. And the design processes of the Blumlein and TLT are introduced. The control strategy of solid state switches is also illustrated. A small prototype is developed to verify the proposed topology. Finally, the threestage generator can produce pulses on matched load （300 Ω） with amplitude of 0~3 kV, pulse width of 100 ns, and PRF to 10 kHz.