A rectangular pulse generator circuit with fast rising and falling edge will be presented in this pa- per. The generator circuit was designed by controlling the quantity of carriers in the middle layer from regulating forward current of the SRD (Step recovery diode), and then indirectly controlling the pulse width. It is based on the principle that large reverse current will °ow through the diode and last for a relatively long time when it is re- verse biased. Experimental results have been analyzed in physical level. They are tallied with theoretical results. The circuit can generate rectangular pulses with rise time about 150ps, fall time about 250ps, amplitude about 10V and pulse width adjustable from 1ns to 10ns in 50 load. The trig jitter is less than 5ps and the amplitude jitter is better than 4%.