Abstract: An experiment was conducted to investigate the breakup processes of round liquid jets in cross airflow with a high-speed video camera.The orifice diameter of the nozzle was 0.3 mm and the liquid used in the test was water.The liquid-to-air momentum flux ratio varied from 10.2 to 80.The results indicate that the initial surface waves are sinuous,which will be developed into spiral waves by aerodynamic force.When the spiral waves grow large enough,the liquid column will be either pinched due to surface tension or cut by aerodynamic force,depending on the cross airflow velocity.The amplitude of the spiral wave is increased with the rising cross airflow velocity.The fluctuations of the liquid jets trajectories are larger for higher airflow velocities,and weaker for higher liquid jet velocities.The correlations between the coordinates of the jet breakup locations and the liquid-to-air momentum flux ratio were concluded.The equation of the trajectory like parabola curve was derived for the jet column trajectory before breakup.