Abstract: In order to find out the invalidation of submicrometer semiconductor devices under different microwave pulses, the author developed a simulation program based on the hydrodynamic method (HDM). Coupled Newton method was used in the program to solve nonlinear equations that describe device properties. The paper has shown the transient simulation results on a one dimensional ballistic diode done by the program, including the electron temperature, electric field, electron and hole densities, etc. When a relatively high voltage (10 V) is applied to the device, the results show great difference from low ones. The author has tried the second breakdown theory on the phenomenon. Further work should be done to get more accurate simulation results and reasonable physical analysis.