The effects of different nitrogen application rate on the yield and forage nutritive quality of alfalfa were studied in an experiment of pot culture. The results showed that under the condition of the same level P and K,the fresh yield and dry yield were both increased by application of nitrogen fertilizer. and the second, the third, the forth harvest stage, the middle nitrogen level（0.18 g·pl^-1）was more markedly responded than the highest nitrogen level（0.36 g·pl^-1）except the first harvest stage, and the yield of the lower nitrogen level（0 g·pl^-1）decreased quickly than the topdressing nitrogen fertilizer. With increasing of clipping times, the middle nitrogen level increased content of crude protein（CP）, ether extract（EE）, crude ashes（CA）, and decreased the crude fiber（CF）,than those of the highest nitrogen level, which improved the forage nutritive quality and the gross energy（GE） of alfalfa. Effects of the different nitrogen level on the forage nutritive quality of alfalfa were embodied in different harvest stage, the middle level reduced the ratio of the crude fiber（CF） and crude protein（CP）, it was reduced by the highest level, and both the middle level and the highest level improved the forage nutritive quality of alfalfa.