Abstract: Photo-thermal characteristics of 4 hybrid rice were determined by comparing the days from sowing to heading under different temperatures and day light.The results indicated that Ⅱyou 3301,Teyou 3301,Minyou 3301 and Tianyou 3301,the four rice varieties hybridized from Minhui 3301,had a weak temperature susceptibility(Grade 1-2),a medium photosensitivity(Grade 4) and a long basic vegetative period(Grade 9).Among them,Ⅱyou 3301 and Teyou3301 had slightly longer basic vegetative period and slightly weaker photosensitivity,and Minyou 3301 and Tianyou 3301 had slightly shorter basic vegetative period and slightly stronger photosensitivity than the others.Ⅱyou 3301,as compared with Teyou 3301,and Minyou 3301,as compared with Tianyou 3301,had slightly stronger susceptibility and photosensitivity.When four hybrid rice varieties were planted in a safe growth season in Fujian,except for double cropping late rice cultivation in Southern Fujian,the day length during photosensitive period was 13-13.8 h.The natural day length did not lead to a significant early or late heading,and temperature was a major ecological factor during the growth period.When the average temperature increased by 1℃,the time from sowing to spike was shortened by 4.6-5.3 d,from sowing to heading shortened by 6.1-7.1 d,and the entire growing season shortened by 8.7-9.7d.