Two seedling age (Y1,15 d and Y2,20 d) and three sowing date (B1:25th June,B2:30th June and B3:5th July) were used to study the effects of sowing date and seedling age on grain yield of late rice with mechanical transplanting.The results showed that the yield of B2 and B1 were no significantly different,but 8.7% and 3.5% higher than that of B3.The yield components except 1 000-grain weight decreased with delaying the sowing date.The yield of Hyou 518 and EJ 403 decreased from the highest yield to lowest yield were 45% and 13.5%,respectively.The post-heading biomass accumulation of the former was significantly lower than that of the latter.The yield of Y1 of B2 and B3 was 0.2 t/hm2 higher than that of Y2 except B1,because the booting stage of B1 through high temperature led to a significant decrease of spikelet.The late indica rice under low temperature was more sensitive than the late japonica rice.The former must be sown early for high yield,because the delayed sowing date may be against the grain filling.The latter one for high yield should be sown early to have enough seeds.The seeding age of both should be less than 20 d.Further studies are needed to investigate the physiological changes caused by sowing date and seeding age.