Abstract: 4-hydroxycinnamic acid was firstly isolated from Fructus mume and identified to be one of the main components. The studies aimed to investigate the immunotherapeutic potential of 4-hydroxycinnamic acid on SPF chickens infected with IBDV. The results showed that the bird survival rate of 3 dosage groups of 4-hydroxycinnamic acid was 87.5, 62.5 and 42.86%, respectively while body weight gain rate was 25.68, 25.28 and 21.37%, respectively. As for the survival rate and body weight gain, no significant difference was found between 35 mg kg-1 dosage and high immune yolk antibody group (p>0.05). The histopathology score of the high dosage group 3 was lower than that of the high immune yolk antibody group 6. The Stimulate Index (SI) of spleen lymphocytes of chickens fed 4-hydroxycinnamic acid (SI = 1.69) was significantly higher than that of untreated chickens (SI = 1.36) (p<0.05). These results showed that chickens fed with 35 mg kg-1 4-hydroxycinnamic acid for 5 days could effectively induce a high protection against IBDV and its related mechanism may enhance cell immunity.