To understand the effects of self synthesized N-carbamylglutamate (NCO) on growth performance of ICR mice, mice were fed with the basal diet adding with 0.025%, 0.05% and 0.1% NCG for 28 d. Effects of different levels of NCG on body weight of mice were observed. The results showed that the addition of NCG in the feed could improve the growth performance of mice, and the growth-promoting effect enhanced with the increasing dose.