Abstract: This paper used the high speed camera to observe a cylindrical liquid jet into crossflow and to breakup under the action of wave developments.A direct nozzle has been used, of which the outlet diameter is 1mm and the aspect ratio is 20.The liquid jet in the experiment is water and the crossflow is air.The test temperature is 293K, and the liquid jet velocities are from 2 to 20m/s, with Reynolds number from 2400 to 22400.The velocities of the crossflow change from 10 to 40m/s, with Weber number of from 1.6 to 25.6, that is to say the momentum ratio between the air and the liquid is from 5 to 127.The frame of the high speed camera is 2000 and the exposure time is 16s.The experimental studies have found that:the differences of Weber number of the crossflow will change the fragmentation behavior of the liquid jet and the dimensionless surface wave length is proportional to the-0.31 power exponent of the Weber number of the crossflow.The distance of the fracture point of liquid column along the direction of the crossflow decreases with the increase of the momentum ratio of the liquid to the air, while it along the initial direction of liquid jet increases with that momentum.The velocity of the droplets produced after fracture on the direction of the crossflow is about 0.1 times as high as that of the crossflow, while it on the direction of initial liquid jet increases linearly with the momentum ratio of the liquid to air firstly, until it becomes 0.8 times of the velocity of initial liquid jet.Based on the above study, this paper had fitted the relation between the wavelength and the Weber number of the crossflow; and also the position of fracture point of the jet, the trajectory of jet, the velocities of produced droplets along with the initial conditions.