The effects of grain number per earhead, 1000-grian weight on grain yield/plant, and the effects of 7 charcters both on grain number per earhead and 1000-grain weight within-sorghum hybrids were analysised in this paper, The results indieated tgat in high yielding hybrid sorghum dreeding the earhead number per mu should sufficiently be ensured, then breeders have to put stress on increasing the grain werght per carhead. For this reason, both the grain number per earhead and 1000-grain weight should be increased. For the middle stem hybrid grain number per ear head were more important than the 1000-grain weight, and for tall stem hybrid the 1000-gcain weight were more important than the grain number per earhgad. In order to obtain more grains per earhead, earhead length is main character to be increased for tall atem hybrid, and delaying of heading date is the main one for middle stem hybrid. In order to increase 1000-grain weight, it is important to prolong the grain milky maturity stage for the tailstem hybrid but for middle stem hybrid to improve content if cutin endosperm and number of leaves.