Abstract Airflow spinning involves a polymer nanocomposite solution composed of nanoparticles and a polymer solution extruded through spray holes and then blown and finely deposited by a high‐speed gas jet onto a mesh curtain to form a composite fiber material. It is widely used in various fields owing to its high efficiency. To investigate the effect of the nanoparticles on the fibers, online high‐speed camera observations were used to capture the dynamics of the liquid jets (liquid jets online and fibers when deposited on the mesh curtain) in the nozzle exit region after the addition of nanoparticles. Because the initiation and propagation of a liquid jet are three‐dimensional processes, two orthogonal planes that can provide a large amount of information regarding the motion of fiber particles were selected for observation in this study. The results indicated that the difference between the liquid‐jet diameters observed in the two planes was approximately within 20 μm. The nanoparticles accelerate the decay of the liquid‐jet diameter to different extents. Moreover, it increases the probability of defects such as shots. Additionally, we studied the effects of different nanoparticle sizes and concentrations on liquid‐jet dynamics. A new explanation for shot formation was proposed. The findings of this study provide valuable insights into the three‐phase flow in the field of spinning and a solid experimental foundation for the development of composite fibers. Highlights The diameter of the liquid jet differs by 10–20 microns in two planes. First study of three‐phase flow with nanoparticles in air spinning. Explained “shots” formation through experiments and simulations.