To study the effect of circulation small peptides concentration on mRNA expression in small intestine, graded amount of soybean small peptides (SSP) were infused into lactating goats through duodenal fistulas. Peptide-bound amino acid (PBAA) concentration in arterial plasma and the mRNA expression of PepT1 was detected in the current study. The results showed that concentrations of all peptidebound amino acids (PBAA) increased and the activity of PepT1 in duodenum tissue was enhanced by SSP infusion. The PepT1expression in duodenum tissue was significantly increased with the increment of amounts of SSP infusion (P<0.05). That in ileum tissue was increased with the increment of the amounts of SSP infusion; the increment of Pep T1 expression was significant only in the 180 g/d treatment (P<0.05). mRNA abundance of PepT1 in jejunum tissue was 1.1 to 1.8 to 2.4 times in SSP infusion group as compared with the control group. In the 120 and 180 g/d treatment, the difference of PepT1 expression in jejunum was significant (P<0.05). The data suggested Pep T1 expression in duodenum, ileum and jejunum tissue was enhanced by an increase in circulation small peptide concentration, and the duodenum might be a main position of small peptides absorption in intestine.