To determine the basic features and influence mechanisms of a gas flow field in the atomization chamber at the nozzle outlet of a vortical loop slit atomizer, a computational fluid dynamics-based numerical simulation of this gas flow field was conducted under different annular slit widths, gas pressures, and protrusion lengths of the melt delivery tube. At a pressure P = 4.5 MPa and protrusion length H = 4.5 mm, a great annular slit width D corresponded to a small aspiration pressure. A low aspiration pressure contributed to the smooth downward flow of metal melt and a stable atomization process. When D = 1.2 mm and H = 4.5 mm, and pressure satisfied 2 MPa <= P <= 4 MPa, a high pressure corresponded to a high aspiration pressure. However, the maximum backflow velocity of the gas on the axis in the flow field center and the maximum radial width of the recirculation zone were approximate, thus limiting the improvement effect on atomization performance. The aspiration pressure increased when the pressure exceeded 4 MPa. The maximum backflow velocity of the gas on the axis in the flow field center and the ma vimum radial width of the recirculation zone increased rapidly, thus effectively improving the a to mi:atio n performance. When D = 1.2 mm and P = 4.5 MPa, a great protrusion length H corresponded to a low aspiration pressure, and the maximum radial width in the recirculation zone exhibited a stable fluctuation after dropping rapidly; this phenomenon does not benefit the improvement of atomization performance.