The characteristics of the pressure distribution and Mach disk position are analyzed for simple nozzle and complicated nozzle based on Hall design method, and the difference of dynamic characteristic of gas flow is compared particularly. The trend is revealed that the difference of dynamic characteristic between the two nozzles becomes smaller with the increase of working pressure. It is demonstrated that using the simple structure nozzle to replace the complicated flow line structure nozzle is feasible for decreasing the cost of laser cutting under the high pressure condition.