Among the bacterial diseases of the aquatic animals, Aeromonash ydrophila is one of the known pathogenic factors in fish causing complications such as fin rot, skin sores, and deadly haemorrhagic septicaemia. Therefore, the use of vaccines along with various synthetic and natural adjuvants for better immunization against this disease is important and is examined in different studies. In this study, the bacterial effects of Aeromonas hydrophila along with Freund adjuvant on the expression rate of lysozyme-c gene in the anterior kidney tissue of the common carp fish (Cyprinus carpio) were measured. 180 fish specimen with an average weight of 50g were divided up into 3 groups and each group into 3 repetition of 20 specimen to this end. Groups 1 to 3 were respectively immunized by using physiology serum (as control), bacteria without adjuvant and bacteria along with Freund adjuvant in the form of intraperitoneal. Three groups each were challenged with the deadly concentration of Aeromonas hydrophila in the 28 th day of the research. Sampling the anterior kidney tissue was done before the challenge and intervals of 12, 24, 72 hours and also 7 days after the challenge. The expression rate of lysozyme-c in the taken samples was finally measured by doing PCR experiment in the real time. According to the obtained results, the level and the procedure of the studied gene expression in both immunized groups showed a significant increase than the control group (P<0.05). It can generally concluded that immunization by the bacterial Aeromonas hydrophila in carp (Cyprinus carpio) caused an increase in the level and the improvement of the procedure of the gene expression of lysozyme-c after facing the bacterium causing the disease.