Objective To investigate the effect of modified Xiaoyao San on the balance of helper T cell 1（Th1） and helper T cell 2（Th2） on allergic conjunctivitis. Methods Mice model with allergic conjunctivitis induced by ovalbumin（OVA） were randomly divided into model group, modified Xiaoyao San group（including high, medium and low dose group）, positive drug control group（cromolyn sodium eye drops）, another normal group as a blank control, each group had 10 mice so a total of 60, and intervention was given for 2 weeks. Eye signs were observed and serum levels of IFN-γ and IL-4 detected by ELISA. Results Each dose of modified Xiaoyao San could alleviate eye symptoms. The model group had the highest mean sign score, significantly higher than that in the blank control group（P<0.01）, the scores of signs in Xiaoyao San group with different dose were lower than of in the model group（P<0.01）. There was no significant difference between the mean scores of Xiaoyao San group and the scores were closer to that of the Cromolyn sodium eye drops group（P> 0.05）.2. Serum IL-4, IL-4/IFN-γcontent in each dose of Xiaoyao San group and cromolyn sodium eye drops group were lower than that of model group（P<0.01）, but IFN-γwere higher than that of model group; there was no significant difference among high, medium and low dose of Xiaoyao San groups（P>0.05）. Conclusion Modified Xiaoyao San may ease the eye signs in mice with allergic conjunctivitis, and possibly regulate Th1 and Th2 balance.