Abstract: The cutting quality and capacity of an oxygen-propane flame cutting nozzle mainly depend on the characteristics of the cutting oxygen jet. In this paper, the structures of the cutting oxygen orifice of straight cylinder type, conical type, and arc type were investigated. Through theoretical calculations, numerical simulations, and experimental studies, the influence of the cutting oxygen orifice structure on the flow characteristics of the cutting oxygen flow, such as Mach number, velocity distribution, pressure distribution, and density distribution, was revealed. The results show that the straight cylinder type is a subsonic orifice with a maximum Mach number of 1 in jet, and the convergent-divergent (CD) type, namely Laval type, is a transonic orifice that allows the jet to cross from subsonic to supersonic velocities. Compared with a conical type orifice, an arc type orifice has better jet stability, a longer supersonic section, and smaller radial jet fluctuation at the outlet, which is conducive to slag blowing off during the cutting process to obtain better cutting surface quality. Finally, the numerical simulation results are validated through the use of 3D printing techniques and schlieren experiments.