The dence of processing parameters on the air-jet textured(AIT) yarn was investigated to characterize the structural properties of acetate and viscose rayon fibers. The air-jet texturing nozzle employed was Hemaiet manufactured by Heberlein Co., Swiss and the samples were produced with four diffirent air pressures(i. e.,), 4, 5, 6kg/m2), usage of impact ball and dry/wet conditions. The structural characteristics investigated were yarn instability and fiber configurations such as floats, arcs, potrudes, and cross/closed loops. The results obtained though this experiment was as follows: (1) the instabilities of acetate and viscose A/T yarns were increased with raising the air pressure of nozzle and usage of impact ball due to the increase of loop frequency, (2) the texturing effect of regenerated fibers was partially enhanced by the water application and the use of the impact ball due to the decrease of filament friction and the increase of turbulent air flow in the nozzle, and (3) the surface characteristics of acetate and viscose A/T yarns had the stable loop structure with increasing the air pressure of the nozzle and water application.