Two Schiff bases of chitosan (CTS) were synthesized from 4-methoxylbenzylaldehyde (CH3O-CTS) and 4-methylbenzylaldehyde(CH3-CTS). The Schiff bases were characterized by FTIR, DSC-TGA, solid 13C CP-Mas NMR, and elemental analysis. Antibacterial activities of the Schiff bases against Escherichia coli and Staphylococcus aureus were measured by the optical density method. The antibacterial activity of the Schiff bases is better than that of the original CTS. The IC50 of CH3O-CTS and CH3-CTS against Escherichia coli is respectively 40.3 ppm and 43 ppm, which being 38.5 ppm and 39.5 ppm against Staphylococcus aureus, lower than IC50 of chitosan, being 59.5 ppm and 52 ppm against Escherichia coli and Staphylococcus aureus, respectively.