The objective of this study was to investigate the regulatory effect of rutin on lactation of rats by examining the effects of a natural plant extract rutin on milk yield, endocrine hormones and organ indices of rats. Eighteen pregnant Wistar rats were randomly assigned to 3 treatments: control, gastric infusion of rutin at 60 mg/kg BW per day, and intramuscular injection of estradiol 60 μg/kg BW weekly from the fourth lactation day for two weeks with the same basal diet. The milk yield of rats, body weight gain of filial rats, mammary gland index, thymus index, spleen index, the levels of estrogen (E2), progesterone (P), prolactin (PRL) and growth hormone (GH) in plasma and gland tissues were measured. The milk yield of the rats receiving rutin was higher than that of the control group (P＜0.05), but lower than that of the estradiol group (P＞0.05). The body weight gain of the progeny from the rats receiving rutin was higher than that of the control group (P<0.05), but lower than that of the estradiol group (P＞0.05). The levels of E2, PRL and GH in plasma and gland tissues of the rats receiving rutin was higher than that of the control group (P<0.05), but less than that of the estradiol group (P<0.05), and the differences of P level among groups were not distinct (P＞0.05). The indexes of mammary gland, thymus and spleen of the rats receiving estradiol were higher than those receiving rutin or the control group (P<0.05). In conclusion, dietary rutin significantly improves the milk yield and accelerates growth of the thymus and spleen of rats.［Chinese Journal of Animal Nutrition, 2010，22（6）:1775-1782］