Grain development on wheat spike is asynchronous.The grain number and grain weight in different positions significantly varied with wheat cultivars and plant densities.The experiments with two winter wheat and four plant densities were conducted at Taian experiment station of Shandong Agricultural University from 2010 to 2012.The results showed that the grain number,spikelet weight,and grain weight with the spikelets positions from the bottom to the top increased first and then decreased,showed parabolic change.And this is accord with medial dominant in grain development.The differences of seed-setting traits between two cultivars were significant.Meanwhile,seed-setting traits of main spike were superior than that of tiller spike.Under low sowing density,the seed-setting traits and grain weight in Wennong6 were more superior than those in Jimai20.and those of main stem spike were more superior than those of tiller spike.The effects of spikelet and grain positions on the weight of individual grain varied with the grain number of spikelet.For both two cultivars,in the bottom 2 grain-set spikelets,the grain weight in the second grain position (2nd)position was the higher than that in the first grain position (1st),whereas it was inverse for the upper and top 2 grain-set spikelets.For Wennong6,in the bottom and middle 3 grain-set spikelets,grain weight in 2nd position was the highest followed by that in 1st,and the third grain position (3rd),while grain weight in 1st＞2nd＞3rd for the upper 3 grain-set spikelets.For Jimai20,in all 3 grain-set spikelets,grain weight in 2nd position was the highest followed by that in 1st,and then in 3rd.For 4 grain-set spikelets of Wennong6,the grain weight in 2nd position was the highest,followed by that in 1st,3rd(,) and the four grain position (4th) was the smallest.Different from the genotype,there was less 4 grain-set spikelets in Jimai20.The seed-setting characteristics in main stem spike are relatively stable.Plant density affects the yield through controlling the seed-setting characteristics in tiller spike.In the wheat production,we should properly increase plant density to keep reasonable tiller spike,and increase the seed-setting rate by decreasing the sterile spikelet in basal and top spikelets,and develop the potential of grain weight in the 3rd and 4th grain positions on the basis of ensuring that in the 1st and 2nd grain positions of spikelet.