Abstract: Hybrid rice，“Shanyou 63”，of which the yields are from 7.1 to 15．5t／hm²，is used to analyze the relation between the yield and its components．and its determinants．The results show that grain yield is mainly determined by the number of spikelets and filled grains per m²． When grain yield is less than 12t／hm²，it increases with the increase of spikelets per panicle：when it is more than 12t／hm²，it increases with the increase of panicles per m²．When the number of spikelets per m² is less than 55000，the number of spikelets increases with the number of spikelets per panicle．Conversely，it increases with the number of panicles per m²．The relationship between weight of grains per panicle and the number of spikelets per panicle is of positive correlation．The weight of grains per panicle increases by 0．0241g with the increase of one spikelet per panicle．