The nitrogen budget of GIFT strain of Nile tilapia fed with three types of diets(Europe,"Dajiang", Tilapia farm made) was determined and compared by biological method, while excretive nitrogen was determined and compared by chemical method. The results showed that the specific growth rate and food conversion rate were both very significantly affected by diet types(P<0.01). Nile tilapia fed with "Europe"diet had the best growth. From the aspect of allocation of intake nitrogen, Nile tilapia fed with "Dajiang" diet had the highest utilization proportion of nitrogen for growth. The nitrogen budget of tilapia is affected by the quality of protein, energy content and nutrition equilibrium of feed. It is key issue to improve feed quality to reduce aquacultural pollution.