Pot and field experiments were conducted to study the dosage and the effect of compound nitrogen fertilizer synergists combined with different dosage of urea on the growth,yield,uptake and nitrogen use efficiency of rice with()~(15)N-labled.The results showed that the growth of rice seedling was obviously promoted with appropriate dosage of compound nitrogen fertilizer synergists(20% of N).Treated with urea and added with compound nitrogen fertilizer synergists,the growth of rice wasn't affected,the Ndff%,the total()~(15)N uptake and total nitrogen uptake of rice and the nitrogen use efficiency were increased.Treated with urea reduced by 5%~15%(7.8~23.7 kg/hm~2) and added with compound nitrogen fertilizer synergists,the growth,yield,and nitrogen content of rice were not affected,the total()~(15)N uptake and total nitrogen uptake of rice were the same as CK_2 or higher than it,and the nitrogen use efficiency,physiological rate and agronomic use efficiency of nitrogen were remarkably increased comparing to CK_2.Treatment with urea reduced by 30% and compound nitrogen fertilizer synergists,the growth and absorption and utilization of nitrogen of rice were apparently decreased.As a result,treated with appropriate dosage of compound nitrogen fertilizer synergists(20% of urea),the growth and yield of rice were not affected,the utilization of nitrogen was enhanced and the dosage of nitrogen fertilizer was decreased by 15%.