Sixty varieties of Japonica Rice were grown under normal condition to study the correlations among the length, width and area of the sword leaf and grains weight per spike. The results showed that the number of grain per spike was positively correlated with the width and area of the sword leaf, but negatively correlated with the length. The correlation between the number of grain per spike and the width of the sword leaf was significant and larger than that between grain number and area of the sword leaf. 1000-grain weight was significantly positively correlated with the length and area of sword leaf, but not significantly correlated with the width of sword leaf. The grains weight per spike was significantly positively correlated with the width and area of sword leaf. Whereas the correlation between grains weight per spike and length of sword leaf was not significant. The results indicated that the size of the sword influenced grains weight per spike. So we should pay attention to raising the area of the sword leaf in rice breeding and cultivation.