Drift step recovery diode (DSRD) has a great application prospect in pulse power technology for its notably short switching-off time, high repetition rate and large working current. In this paper, a DSRD pump circuit topology based on magnetic saturation transformer is studied. The topology is small, light and reliable. According to the operating requirements of DSRD, a pump circuit was designed. It consists of a power MOSFET primary switch and a magnetic saturation transformer with boost and saturation characteristics. The circuit was simulated by Pspice software, which confirmed the principles of the circuit. Based on the simulation analysis, a prototype was designed and its circuit experiment was implemented. The experiment indicates that when the charging voltage is 800 V, the pulse amplitude on resistor load of 50 Ω is larger than 7 kV, the rise time is less than 4.2 ns (10%?90%) and the FWHM is about 10 ns.