Abstract: Photo-thermal characteristics of the hybrid rice,Tianyou 3301,were studied.By comparing the number of days from sowing to heading under different temperatures and day-lengths,as well as an indexing method of using the number of days from sowing to heading under high-temperature-short-day-length conditions,the ecological characteristics of the rice were obtained.The results indicated that Tianyou 3301 had a weak temperature susceptibility(Grade 1-2),medium photosensitivity(Grade 4) and long basic vegetative period(Grade 9).When Tianyou 3301 was planted in safe growth season in Fujian,its photosensitive day-length generally exceeded the critical day-length for promoting heading,and temperature was a determining factor for its growth.When the average environmental temperature increased by 1℃,the vegetative growth stage was shortened by 4.4 d,and the growing season reduced by 8.4 d.The days of field vegetative growth stage and sun exposure during its ripening period were important ecological factors affecting the yield of the rice.