In this paper, the working principle of drift step recovery diode (DSRD) is introduced. The relation between the device parameters and switching characteristic is revealed by studying the physics processes inside DSRD. The analyses show that the rising rate of output pulse is proportional to the electric field breakdown threshold and saturated drift velocity of carrier. Large breakdown threshold and low doping level are benefitial to improve the maximum operation voltage, but the switching time will be increased also. In general, high breakdown threshold is necessary for DSRD with excellent performance. In addition, for the expanding of the diffusion zone over time, the pre-pulse can be reduced with short pumping time, which is obvious when forward current time is larger than 200 ns. To obtain an ideal pulse front, the injected charge should be exhausted as soon as the backward current just achieves maximum. By a simple pumping circuit, a fast pulse generator based on DSRD with the rise time of about 4 ns and the amplitude of 8 kV was designed, which can be used to trigger the fast ionization diode.