Abstract: Taking japonica indica hybrid late rice variety of Yongyou 2640 as material，field experiments of mechanical transplanting late rice were conducted under different sowing date in Jinhua，Zhejiang province in 2012 and 2013.Based on experiment and meteorological data，the effects of sowing date on growth characteristics and grain yield of late rice were analyzed.The latest suitable sowing date of the late rice variety was studied under mechanical transplanting method in the research area.The results showed that，with the delay of sowing date，whole growing days of late rice were initially decreased and then increased，sowing full heading days were initially decreased and then increased in the year of cold air activity early in fall，and they were decreased when cold air activity late.Yongyou 2640 showed heterosis，with maximum grain yield 9964.5kg/ha and maximum population spikelets 44512.5×10 4 No./ha. Grain yield of late rice was decreased with the delay of sowing date，seed setting rate was influenced obviously by sowing date，so it was the key influence factor of grain yield variation.Population of spikelet was less influenced by sowing date，and 1000 grain weight was less influenced.The fertility of late rice was reduced if it met low temperature during booting to heading stage，but it had certain tolerance ability to low temperature，negative accumulated temperature of 23℃ in 25 days before full heading date was the most sensitive low temperature factor，the condition that negative accumulated temperature of 23℃ was not greater than 16.6℃·d could ensure stable yield of late rice.The final date of negative accumulated temperature of 23℃ less than 16.6℃·d under the 80% assurance rate was regard as safe full heading date，so the latest suitable sowing date of Yongyou 2640 was from June 29 to July 2 as mechanical transplanting late rice.

Key words: Mechanical transplanting, Yongyou 2640, Sowing date, Grain yield, Safe full heading