This trial was conducted to study the effects of N-carbamoylglutamate (NCG) on growth performance, nutrient digestibility and serum free amino acids of weaned piglets. Sixty 26-day-old weaned piglets with average weight of (6.4±0.7) kg were randomly divided into 4 treatments with 5 replicates in each treatment and 3 piglets per replicate using a randomized complete-block design, and then were fed one of four diets containing 0, 0.04%, 0.08% and 0.12% NCG, respectively. The results showed as follows: 1) with the increase of NCG supplementation, ADG and F/G of weaned piglets in every stage expect 26～40 days of age were improved in quadratic rule (P<0.05), and 0.04% or 0.08% NCG supplementation significantly improved ADG and F/G of piglets (P<0.05); 2) NCG supplementation enhanced diet protein and phosphorus digestibility (P>0.05); 3) diarrhea ratio and diarrhea index of 0.04% NCG group were lower than those of the control group (P<0.05), but 0.12% NCG, compared with 0.04% NCG, increased diarrhea ratio and diarrhea index (P<0.05); 4) linear increasing trend was observed in free arginine content in serum when NCG was supplemented to diets of piglets （P=0.077）, and free arginine content in serum of 0.08% and 0.12% groups was higher than that of the control group (P<0.05). In conclusion, the growth performance and diarrhea index of weaned piglets were improved by 0.04% or 0.08% NCG supplementation. Considering growth of piglets and cost of NCG, 0.04% was an appropriate and feasible level for NCG supplementation of weaned piglets.［Chinese Journal of Animal Nutrition, 2010，22（4）:1012-1018］