Abstract: Flying is one of the important indexes in cellulose acetate quality evaluation. In order to study qualitatively the flying and the mechanism of its generation in the production process of cellulose acetate, MALLS-GPC, DSC and SEM were used to characterize the flying. The results showed that molecular weight and its distribution, the synthesis process of cellulose diacetate, the gel component and titanium dioxide particles in spinning dope, and the fluctuation of spinning technical conditions were main factors responsible for the generation of flying.