Abstract: Three different rice cuhivars，characterized by 3 larger panicle type，such 3S new plant type rice“IR_65600.85”、“Peiai64S／E32”and“Eryou86”are used in the experiment to investigate the grain-filling characteristics and the changes 0f the relevent physioehemical activity．The results show that the superior grains of rice in each entry have higher initial growth power than the inferior grains，in turn entering active grain-filling stage earlier；the superior grains also perform higher activities of ADP-glucose pyrophosphorylase and starch synthase than the inferior grains in each entry during the early stage of grain-filling，it is helpful to promote the transpo rtation of dry matter into the superior grains；there are differences in genotypes in the case of the physiochemical activities ，among the three rice cultivars concerned，“IR_65600.85”exhibits its poor physiochemical activities ，consequently decreases percentage of filled grains and yield．