Abstract: The effects of nozzle screw structure on liquid jet breakup were investigated with a high-speed camera. Five nozzles with different diameters (4.00, 4.80, 7.50, 8.75 , 10.80 mm) were used in the experiment. The thread depth range was 0.40—1.25 mm, the liquid jet Reynolds number (Re) was within the scope of 500—22600, and the Weber number was within the scope of 0.0003—1.2000. The experimental results showed the screw structure had a strong disturbance to the jet and promoted the breakup of jet. By comparing the jet breakup length under different experimental conditions, it could be obtained that increasing Re led to the decrease of breakup length when Re<1 600. The structure of nozzle screw had little influence on the breakup length of liquid jet. The breakup length of liquid jet increased first and then decreased with Re raised. In this condition, the influence of screw structure of nozzle was significant, the breakup length was shorter than that of the smooth one. When Re>7 000, the breakup length of liquid jet rised with the increase of Re and the screw structure of nozzle continued to promote the decrease of the breakup length of liquid jet. The experimental results showed that the influence of nozzle screw structure on small diameter nozzle (diameter less than 5 mm) was more significant than that on the larger nozzle. By using dimensionless thread depth, Re and Weber number, the relationship for predicting the breakup length of liquid jet was established.