The study was conducted to investigate the effects of dietary selenium sources and vitamin E levels for sows on organ indices and serum hormone levels of their neonatal and weanling piglets. A 2×2 double factories design with two levels of vitamin E (30 and 90 IU/kg) and two kinds of selenium sources[sodium selenite (SS) and selenium yeast (SY)] at 0.30 mg/kg (calculated by selenium) was used. And a total of 296 Landrace×Yorkshire multiparity sows with 3 to 8 parities were allotted to four groups with 76 replicates each and 1 sow in each replicate according to parity and body condition. Four groups were 0.30 mg/kg SS+30 IU/kg vitamin E group, 0.30 mg/kg SS+90 IU/kg vitamin E group, 0.30 mg/kg SY+30 IU/kg vitamin E group and 0.30 mg/kg SY+90 IU/kg vitamin E group, respectively. The experiment was lasted from the first day of sow breeding to 21 days of age when piglets were weaned. On the day of farrowing and weaning, 8 piglets (1 pig in each nest, with similar body weight to the nest average weight, and 4 males and 4 females) from each group were selected, and after weighing, the blood was sampled to prepare serum samples, then serum levels of insulin (Ins), glucagon (Glu), triiodothyronine (T₃), tetraiodothyronine (T₄) and insulin-like growth factor-1 (IGF-1) were determined. After the blood collection, the pigs were slaughtered, and the heart, liver, spleen, kidney, pancreas, thymus, thyroid and other organs were separated and weighed. The results were showed as follows:1) compared with SS supplementation, SY supplementation in sow's diets had no significant effects on organ indices of neonatal piglets (P>0.05), but significantly increased the thyroid index of weaned piglets (P<0.05), extremely significantly decreased thymus index of weaned piglets (P<0.01), significantly increased serum Ins and T₃ levels (P<0.05) and had a trend to improve serum IGF-1 level (P=0.086) of neonatal piglets, extremely significantly lowered serum Glu and T₄ levels of neonatal piglets (P<0.01), and significantly lowered serum T₄ level of weaned piglets (P<0.05). 2) Compared with supplementation of 30 IU/kg vitamin E, supplementation of 90 IU/kg vitamin E in sow's diets significantly increased pancreas and thymus indices of neonatal piglets (P<0.05), extremely significantly increased spleen index (P<0.01) and had a trend to increase pancreas index of weaned piglets (P=0.056), significantly lowered serum Glu level of neonatal piglets (P<0.05), and had no significant effects on serum hormone levels of weaned piglets (P>0.05). 3) The interaction between selenium source and vitamin E supplemental level significantly affected thymus index of neonatal piglets and serum T₄ level of weaned piglets (P<0.05). In summary, different dietary selenium source and different dietary vitamin levels during sow gestation and lactation period can affect the development of visceral organ of neonatal piglets and weaned piglets, and dietary SY can improve serum levels of IGF-1, Ins and T₃ of neonatal piglets compared to dietary SS. In addition, SY and vitamin E can promote mutually to transform serum T₄ to T₃ of weaned piglets.