The inhibitory effects of ten C3,6-dibenzoylated phenyl-thiosemicarbazone-chitosan derivatives on four species of animal pathogenic bacteria and four kinds of plant pathogenic fungi were studied. The antimicrobial activity of all derivatives is superior to that of raw chitosan.The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the derivatives against Escherichia coliwere 7.40 µg·mL-1and 14.80µg·mL-1respectively. The bacteriostatic effect of derivative on Gram-negative bacteria is stronger. All of the derivatives had a certain antifungal effect on the tested fungi in the concentration range of 0.05 mg·mL-1-2 mg·mL-1, with a maximum inhibition index of 100%. The antimicrobial action of the derivatives increased with the increase of concentration.