The influences of the turbulent properties of the air stream on the liquid jet disintegration mechanism and on the spray characteristics of twin-fluid atomization were investigated. Spray characteristics were measured by the image processing system in the vicinity of the liquid nozzle, and farther downstream they were measured by PDA. Just below the nozzle exit the air velocity fluctuations promote the protrusions of the liquid jet surface. At large turbulence intensity of the air stream the protrusions get larger than those at small turbulence intensity, and the liquid jet disintegration takes place pulsatively. Then large liquid clumps are generated pulsatively, and they are disintegrated again into small droplets downstream. In the vicinity of the liquid nozzle, the diameters of spray droplets generated at large turbulence intensity are larger near the center of the spray than those generated at small intensity, and in the periphery they are smaller. The fluctuation of droplet velocity increases, and the droplet dispersion also increases with increasing air velocity fluctuation. In the region near the liquid nozzle exit, the fluctuation of droplet velocity is almost homogeneous same as the air velocity fluctuation. On the other hand, farther downstream the axial component of the drop velocity fluctuation increases, and the radial one decreases slightly.