[Objective] To explore the effect of reducing dietary protein level on plasma hormones associated with growth and microbiota in digesta of ileum and cecum in weaned piglets. [Methods] Fifty-four selected weaned piglets with similar body weight were assigned to three groups with three diets, each diet contained 20% CP, 17% CP or 14% CP supplemented with Lys, Met, Thr and Trp, according to NRC (2012) recommendation. At day 10, 25 and 45, blood samples were collected from jugular vein of six piglets in each group for analysis of blood parameters and hormones associated with growth. At day 45, we collected the digesta from ileum and cecum for microbiota and its metabolites analysis. [Results] At day 25 and 45, diets with 17% CP and 14% CP decreased the concentration of blood urea nitrogen compared to control group (P<0.05). Low protein diets with 14% CP increased the cholesterol concentration at day 45 and increased the concentration of triglyceride at day 25 (P<0.05). But dietary protein level had no effect on glucagon, growth hormone, insulin, T₃ and T₄ in different time point (P>0.05). In phylum level, Firmicutes were dominant bacteria in ileum and cecum, however dietary protein level had no significant effect on the relative abundance of Firmicutes (P>0.05). Reducing dietary protein level tended to increase the relative abundance of Lactobacillus and decreased the relative abundance of Clostridium_sensu_stricto_1, but data was not significant (P>0.05). Reducing dietary protein by 3% or 6% significantly decreased the concentration of ammonia in ileum and cecum (P<0.05). [Conclusion] Low-protein diet with 17% CP or 14% CP had no effect on the concentration of hormones associated with growth, whereas, it decreased the blood urea nitrogen and ammonia in digesta and tended to increase the relative abundance of Lactobacillus. The findings suggest that reducing dietary protein level increase the utilization of nitrogen and contribute to intestinal health.