Based on the monthly rainfall data of 629 stations from 1950 to 2000, using Z index as the standard division of the drought/wetness of seven classes (grades) are made. After squaring mainly agricultural areas in the north of the Changjiang River, the square measure of drought has happened by calculating how much proportion the drought station held each square. The results indicated that the drought areas with constantly extensive tendency are in Jan., Feb., Apr., Jul., Aug., Sep., Nov. and Dec. but declined in June.