The relations between leaf temperature with water condition and yield composition in boot stage on rice were studied in this paper. It shows that the air temperature is higher than leaf temperature. The volume of transpiration has the same trend with leaf temperature. The lower leaf water potential lead higher leaf temperature and lower transpiration with the different water condition. Water potential of leaf reflected crop water condition. The lower water potential of leaf the higher leaf temperature .Crop water condition is suggested by leaf temperature and the volume of transpiration from 11:00 to 15:00 with the solar radiation variation. The weight of per spike has a maximum reduction by water stress at this stage, the following reductions are seed rate and the seed number per spike, and the spike length is the same as control by the treatment time of one day and few hours to the first and the second treatment respectively, and the leaf temperature is higher 1.4~1.8℃ than control. The boot stage was sensitive to water stress.
