In the present study, levan-polystyrene graft copolymers weresynthesized. Levan was obtained from Bacillus licheniformis straincultivated on medium with ammonium chloride as a more conve-nient nitrogen source than regular organic sources. This study isthe first to report the optimized grafting reaction between levanand polystyrene. The influences of different factors – temperature,atmosphere, reaction time, amines and ascorbic acid concentration– on the grafting reaction were investigated, and the mechanismof the grafting reaction between polystyrene and levan was sug-gested.