To investigate the influence of pressure on the atomization characteristics and dust suppression efficiency of internal-mixing nozzles, experiments were conducted using a custom-built spray dust suppression platform. The study examined the atomization behavior and dust suppression efficiency within the pressure range of 0.15 MPa to 0.4 MPa for both air and water, aiming to elucidate the mechanisms by which two-phase fluid pressure affects nozzle flow rate, atomization angle, droplet size, and dust suppression performance. The results demonstrate that, under constant water pressure, as air pressure increases, air consumption rises almost linearly, while water consumption decreases exponentially. The atomization angle progressively narrows, and the droplet size metrics decline accordingly. When air pressure is further elevated, the rate of droplet size reduction diminishes, and the droplet size distribution becomes more concentrated. As air pressure increases from 0.15 MPa to 0.4 MPa, air consumption increases by 47.5 L/min, water consumption decreases by 0.61 L/min (a reduction of approximately 83.56%), the atomization angle reduces by 38°, and D[3,2] decreases by about 54 μm. Under constant air pressure, increasing water pressure reduces air flow and increases water flow, leading to a widening of the atomization angle. However, further increases in water pressure weaken the gas-liquid interaction, causing the atomization angle to decrease once more. The droplet size distribution broadens, and the frequency peak shifts downward. When water pressure rises from 0.15 MPa to 0.4 MPa, air flow decreases by 10.2 L/min, water flow increases by 0.94 L/min, the atomization angle increases by 16°, and D[3,2] increases by approximately 31 μm. Increases in either air or water pressure result in an initial rise followed by a decline in dust suppression efficiency for both total and respirable dust. Based on an analysis of the effects of pressure on nozzle flow rate, atomization angle, and droplet size, the optimal combination of water and air pressures was identified as PL = 0.3 MPa and Pair = 0.25 MPa. Under these conditions, the dust suppression efficiency for total dust and respirable dust reached 71.99% and 45.96%, respectively.