Abstract: The relationship between weather data and early and middle rice yield components over middle and lower reaches of Yangtze River from 1981 to 2003 is analyzed .Percentage of undeveloped grain of early rice increase as mean precipitation rise and as mean maximum temperature decrease at the stage of flowering , premilk and late milk; the relation is clear between Percentage of undeveloped grain of middle rice and agro-meteorology at flowering stage: it goes up as mean precipitation and mean maximum temperature rise. Percentage of partially grain of early and middle rice has the increasing trend with the rise of mean precipitation and fall of mean maximum temperature at late milk stage. Thousand grain weight of early rice goes up with the increase of mean maximum temperature and the decrease of mean precipitation at the stage of premilk and late milk; that of middle rice has the increasing trend with increase of mean maximum temperature and the decrease of mean precipitation at the stage of late milk.

Key words: mean maximum temperature, mean precipitation, percentage of undeveloped grain, percentage of partially developed grain, thousand grain weight