In research of the potential use of chitosan (Cs) as a food additives and the improvement in solubility of Cs, a graft copolymerization in chitosan (Cs) and propionic acid (Pa) was done to obtain Cs derivatives. The deacetylation of Cs was obtained at 98.7%. Viscosity average MWs of Cs, CsPa0.5, CsPa1, CsPa2 were 9.8×10 5 , 3.4×10 6 , 3.5×10 6 and 3.8×10 6 , repectively. The experimental results of antimicrobial activity in the disc diffusion method at 1000 ppm were following: CsPa2 demonstrated the best in Staphylococcus aureus and Bacillus cereus, CsPa1.5 performed best in Escherichia coli and CsPa1 showed best performance in Bacillus subtilis. Also, the results of antimicrobial activity using Cs derivatives in Staphylococcus aureus, Escherichia coli and Bacillus subtilis at 1000 ppm declined as in order: CsPa2>CsPa1>CsPa0.5>Cs>Pa. Furthermore, when Cs derivatives were applied to Bacillus cereus, the antimicrobial activities at 1000 ppm were demonstrated 100%, 100%, 98.4%, 80.6%, 40.7% (in order of CsPa2, CsPa1, CsPa0.5, Pa, Cs).