Hydrogen production in vehicles is underway using plasma discharges working in high pressure conditions of over 1.5 atm. In this system, no production of CO x is expected. The original fuel for the system is methane (CH4) or propane (C3H8). For those purposes, mainly dielectric barrier discharge nonthermal plasma system is employed with a high voltage pulse of width 5–30 $\mu \text{s}$ and a maximum amplitude of 13 kV. The decomposition rate depends on the input pulsewidth; here, a 5–30- $\mu \text{s}$ width pulse is tried, but each pulse is composed of multiples of fundamental 5- $\mu \text{s}$ pulse. Up to a 20- $\mu \text{s}$ width, the decomposition efficiency increases, but above that value, it decreases. The physical phenomena of the pulsewidth dependence depend on the life time of plasma produced by each pulse.