The gas jets from the conical and new designed supersonic nozzles on different working pressure are simulated by a computational fluid dynamics code, FLUENT, using standard k-ε model and unstructured grid finite volume method with compressible axis-symmetry N-S equation. Under the same condition of pressure-inlet, the distribution of symmetry velocity and that of static pressure are compared. The result of the analysis indicates that conical nozzle outlet can reach subsonic or sonic flow. It is fit for low speed and low pressure situation. The gas jet from the new design supersonic nozzle working at design work pressure has better properties than those of other nozzles. So it is better for thick-plate and or high-speed laser cutting. It is obvious that the results of CFD numerical analysis are consistent with the shadowgraph. Thereby it is an effective way to optimize the nozzle according to the performance of flow field.