In order to accurately analyze the secondary atomization phenomenon during fire-fighting jets, in this paper, the acceleration, deformation and breakup of droplets after secondary atomization are studied experimentally, and the characteristics of droplets after secondary atomization are studied. The critical flow rate of secondary water atomization was obtained. By analyzing the relationship between the factors affecting the secondary atomization characteristics and the number of atomized particles in the mixed crushing mode, the results show that the breaking angle decreases first and then increases with the increase of the we number; When 45 < we <60; the breaking angle is less than the average level, and the instantaneous breaking velocity decreases; The bag diameter before bag-like breaking generally decreases with the increase of the number of broken particles. The relationship between the characteristic quantity of atomization quality and the we number provides an experimental research basis for improving the fire extinguishing efficiency.