Some physiological characteristics of new rice varieties after space mutation in flags related to translocation of photosynthate were compared with their original cultivars in the stage of grain filling. The activity of ATPase was increased. The activity of FBPase was decresed. The accumulation of sucrose content in the daytime was lower. The accumulation of starch content in the daytime was higher. The total photosynthate transported out from leaves in the night time was higher. (1 000)-grain mass and filled grain mass per spike of rice were positively correlated to the starch increase of flags in the morning and the total photosynthate decrease of flags in the night, but negatively correlated to the sucrose increase of flags in the morning.