Abstract: Three japonica rice varieties， including glabrous japonica rice Jia 58， hairy\|leaved japonica rice Jia 33 and Xiushui 134， were used in this paper to analyze the filling characteristics of differently\|positioned grains within a panicle by fitting Richards growth equation. It was found that the initial grain filling rate （R0）， max grain filling rate （Gmax）and mean grain filling rate （Gmean） of the same\|positioned grains had shown significant differences between glabrous and hairy\|leaved japonica rice， and the days holding the max filling rate （tmaxG） and active period （D） of Jia 58 got shorter than those of hairy\|leaved japonica rice Jia 33 and Xiushui 134. Meanwhile， the grain filling rate of superior grains， medium grains and inferior grains from Jia 58 were higher than those from Jia 33 and Xiushui 134. In addition， there was no significant difference in the parameters of grain\|filling characteristics among superior， medium and inferior grains from Jia 58 during early filling stage， but that from Jia 33 and Xiushui 134 showed significant differences. The results could be used to explain the physiological mechanism of that Jia 58 represented faster maturity， better plumpness and higher seed setting rate than Jia 33 as well as Xiushui 134.

Key words: Jia 58, glabrous japonica rice, hairy\, leaved japonica rice, grain filling rate