Abstract: To investigate the optimum sowing rate for biodegradable tray of hybrid late rice, using‘Tianyouhua 9’as the test material, the research was conducted with the sowing rate of 60, 70 and 80 g/tray. The results indicated that the sowing rate had significant effect on the quality of seedlings raised by biodegradable tray. With sowing rate increasing, leaf age, the number of root per plant,SPAD of penultimate leaf, stem width and the dry weight of seedling decreased; plant height increased; the dry matter amount of leaf, stem and panicle, as well as the harvest index reduced. The less the sowing rate, the faster the roots grew; the earlier the tillering was. The treatment of 70 g/tray had the maximum tiller number and effective tillers. With different sowing rates, the difference between grains per panicle, 1000-grain weight and seed setting rate was not obvious. The yield of 60 g/tray and 70 g/tray increased by 237.75 and 228.15 kg/hm2, respectively, compared with that of 80 g/tray, and the growth rate was 2.97% and 2.85% , respectively. Taken together, the optimum sowing rate for biodegradable tray of hybrid late rice is 60 g/tray.