Abstract: Nine growing wethers of Inner Mongolia white cashmere goats (IMWCG) with the same father, fitted with permanent cannula at the rumen, T-shape cannula at the proximal duodenum and terminal ileum were used to investigate the effect of rumen-protected amino acid (RPAA) products on nitrogen metabolism in IMWCG. The experimental goats fed diet with the same nitrogen (CP 9.93%) level of a diet consisted of hay(70%), corn(19.65%) and soybean meal(4.5%), were divided into three group in a free random block design as follows: rumen protected amino acids group (group A), normal amino acids group(group B), and control group(group C). Total collection of feces and urine was performed every 24h for 5d. The results showed that supplemental rumenprotected methionine (RPMet) and rumenprotected lysine (RPLys) increased nitrogen intake (P<0.05), and retained nitrogen (P>0.05), and had a tendency to decrease urine urea nitrogen excretion (P>0.05). However, plasma free methionine and lysine concentrations were unaffected by supplemental with RPMet and RPLys.