Objective: To determine the oral immunogenicity of B subunit of Escherichia coli Heat-labile enterotoxin expressed in transgenic potatoes. Methods : Transgenic potatoes were made into dry-freezed powder. Mice were administrated weekly with three doses 0.2g, 0.4g and 0.6g powder containing about 30 -50μg LT-B for three time, comparing with the mice injected with 5μg of LT-B from recombinant E.coli. After feeding the test animals, specific antibody in serum and fecal extract of the tested animals were detected by ELISA. Result : Experimental results demonstrated that 45% mices gavaged with transgenic plant had higher or equivalent levels of serum IgG response and fecal extracts IgA than those injected with bacterial LT-B. Systemic immune response and mucosal immune response have increased to approximately the highest values on 56d and declined on 70d after the last immunization. Conclusion: This findings show that oral immunization with transgenic plant could induce LT-B specific mucosal and systemic immune responses .An edible plant vaccine against ETEC could provide a potential means to protect children from ever acute diarrhea.