The study was aimed to prove up the relationship of 1000-grain weight with yield and quality in japonica hybrid rice. 4 BT-type CMS lines and 24 three-line japonica restorer lines with major difference in 1000-grain weight were crossed in p×q incomplete diallele design to study heterosis of 1000-grain weight in F1 hybrids and the correlations between 1000-grain weight of hybrids and their parents with yield and quality. The results were as follow:⑴56.3% of combinations tested had heterosis over their parents mean in 1000-grain weight, and 19.8% of combinations tested had positive super-parent heterosis. ⑵ The correlations of female, male parents and average of parents with F1 hybrids were very significantly correlated in 1000-grain weight（r=0.33**,0.71**,0.78**）. 1000-grain weight character was more greatly influenced by restorer line than by CMS line.⑶1000-grain weight of F1 hybrids, male parents and average of parents had high significant positive correlation with yield per plant of F1 hybrids（r=0.55**,0.47**,0.51**）. The correlation between 1000-grain weight of female parents and yield per plant of F1 hybrids was not significant.⑷1000-grain weight of F1 hybrids and their male parents had high significant positive correlation with brown rice rate, milled rice rate, head milled rice rate, chalky grain rate, chalkiness, grain length and grain width. They had significant positive correlation with endosperm translucency. 1000-grain weight of female parents had high significant positive correlation with chalky grain rate, chalkiness, grain length. It had significant positive correlation with grain width. ⑸The range of 1000-grain weight of hybrid Japonica with high quality and yield was 25.1 g-27.0 g.