Objective Schiff base LLDPE / CS functional packaging films were prepared by a condensation reaction of p hydroxybenzaldehyde and chitosan ( CS) . Methods The optimal conditions of LLDPE / CS films modification were obtained according to [ L₉(3³) ] . Results The optimal conditions were as follows: a reaction temperature of 45 ℃ , a p-hydroxybenzaldehyde concentration of 25% and a reaction time of 12 h. The study on antibacterial activities against Escherichia coli, Staphlococcus aureus and Aspergillus niger indicated that the lowest antibacterial concentrations of schiff base were 0. 1 mmol / cm²,0. 2 mmol / cm²and 0. 3 mmol / cm², respectively, and the antibacterial activities were improved with the increasing contents of schiff base groups on the surface. Conclusion FTIR and¹H NMR showed that there were schiff base groups on the films.