Abstract: Abstract: According to the agronomic requirements for mechanized transplanting technology for hybrid rice, using Tianyou 998 and Wuyou 308 as test materials, the effects of a seedling tray and sowing rate on entwining effect of seedling roots, seedling quality, and machine-transplanted quality were studied by mechanized precision seedling raising field experiments. The results showed that when the sowing rate of bowl-flat tray nursing seedlings exceeds 65 g/tray, flat tray nursing seedlings exceeds 45 g/tray, and narrow row tray nursing seedlings exceeds 36 g/tray, the entwining effects of seedling roots were suitable for mechanized transplanting by using reliable mechanized precision planting technology, such as the "Field Factory Seedling Precision Sowing Machine for Rice" developed by South China Agricultural University. Variance analysis showed that the effects of seedling tray types on the seedling quality were significant. Among the four seedling raising methods of tray nursing seedling, the seedling quality and the regularity of bowl tray nursing seedlings were the best, bowl-flat tray nursing seedlings took the second place, and flat tray nursing seedlings and narrow row tray nursing seedlings were the worst. Similarly, sowing rates showed significant differences on all seedling quality indicators, especially highly significant differences were showed on plant height, seedling stems width, root length, fresh weight of one hundred plants, dry weight of one hundred plants, root weight of one hundred plants, and height ratio mass. It was concluded that the leaf age, the plant height, the seedling stems width, the root length, the fresh weight of one hundred plants, the dry weight of one hundred plants, the root weight of one hundred plants, and the height ratio mass will decrease with the increase of the sowing rate. The interaction effect on seedling quality between seedling tray and sowing rates was not significant. Considering the quality of mechanized transplanting and the agronomic requirements of hybrid rice, the suitable sowing density for bowl-flat tray nursing seedlings and flat tray nursing seedlings were from 65 g/tray to 80 g/tray, narrow row tray nursing seedlings were from 52 g/tray to 64 g/tray, bowl tray nursing seedlings were from 41 g/tray to 50 g/tray.