The effects of incorporating urea-N and Azolla-N on the rice tiller, panicle, grain growing stages and yield and N utilization effeciency were studied with both the 15N tracer and tiller circlet mark techniques in the condition of paddy field.The results of dynamic study on the growing tiller showed that they were quite different among U-2(30, 30kgN/ha urea were incorporated at transplanting and maximum tiller period, respectively ) , U-3 ( 10, 20, 30kgN/ha urea were incorporated at transplanting and after transplanting 20, 45 days, respectively) , A-2 ( 30,30 kgN/ha Azolla were incorporated at transplanting and maximum tiller period, respectively ) and CK. (blank). The total tiller numbers were 4650, 4950, 5790, 4035 thousand plants/ha, respectively.The rate of rice panicle were 81.9%, 78.8%, 69.8%, 74.4% ,respectively.The average grains per panicle were 75.8,80.6, 78.2, 74.7, respectively.But, the tillers, panicles and grains number decreased slowly with the time which tiller occur delaying. The yield of rice was not significantly different between urea and Azolla treatments. The results from two years experiments showed that the utilization effeciency of Azolla-N ( 41.3-48.2% ) was higher than urea-N(28.0-41.9%) as incorporating at transplanting. However, the utilization effeciency of urea-N (45.7-46.2%) was better than the Azolla-N ( 37.5-42.3% ) when incorporating at maximum tiller period. The nitrogen utilization effeciency for U-3,A-2,U-2 treatments in the first cropping season was 47.7-50.6%, 39.2 -45.7%, 37.0-38.8%, respectively.