To investigate the effect of transgenic Bt rice (TT51) exposure on immune system of parental female rats. Methods Wistar rats were divided into Bt rice group, parent rice group and market rice group. All groups were fed on mixture containing 60% rice. Female and male rats were fed for 10 weeks before copulation, and the parental female rats were carried on the immunotoxicity assessment after being weaned. The parental female rats were sacrificed for blood routine, blood lymphocyte typing, NK activity assay, conA induced lymphocyte transformation test, antibody-producing cell assay as well as lymph node lymphocyte typing. Results Statistical significances were observed on spleen lymphocyte typing and cervical lymph node lymphocyte typing between TT51 rice and market rice , and the proportion of B and T cell between parent rice and market rice. There was no significant difference of other functional experiment among various groups. Conclusion Transgenic Bt rice (TT51) did not have adverse effect on the immune system of parental female rats.