A chito-oligosaccharide-O-kojic acid-Mannich base derivative antibacterial agent and preparing method thereof. The method comprises the following steps: (1) mixing N-Methylpiperazine with a chloro kojic acid and reacting the same to obtain a product of a chloro kojic acid-Mannich base； (2) mixing a chito-oligosaccharide Schiff base with the chloro kojic acid-Mannich base and reacting and processing the same to obtain a chito-oligosaccharide Schiff base-O-kojic acid-Mannich base derivative, and performing an amine deprotection reaction and passivation to obtain a chito-oligosaccharide-O-kojic acid-Mannich base derivative.
