Abstract: With japonica rice cv. Nanjing 9108 as material， the differences of grain filling characteristics were studied at different spikelet positions under different nitrogen rates and planting densities. The results showed that there were interaction effects between nitrogen rates and plating densities to grain filling characteristics. At the lower planting densities， the percentage of empty or unfulfilled rice grains could be reduced with appropriate N application rates. The grain filling characteristics of primary branches were superior to the secondary branches, and the grain filling characteristics were decreased in the order of top＞middle＞bottom at different grain positions. The rice sterile grain rate of 2nd position was the highest at the 2nd position in the first branch, and it was the lowest at the 1st position in the second branches.

Key words: rice, nitrogen fertilizer, planting density, grain position, grain filling characteristics