We have been studying the penicillin release effect of chitosan. The chitosan solution was prepared by dissolving chitosan powder into acetic acid and various organic acid solution. The average molecular weight and the degree of deacetylation of the chitosan were determined to be 50,000 and 90%, respectively. The chitosan gel mixed with penicillin was stabilized for one week. Drug release experiments were carried out in the phosphate buffer solution maintained to pH 7.4 by applying HCl. The concentration of penicillin on the absorbance of 290nm was checked and the data of three times tests were averaged. The results showed that the release rate of penicillin increased at higher concentration. From this experiment we knew that chitosan and its derivatives can be applied to the our other medicine release system.