The scientific application of an ideal rotation system on paddy fields, has now been considered as a very important problem for ensuring higher grain yields and promoting soil fertility. As the commencing work on rotation researches, authors had selected to study the Rice-Cotton, rotation system in Yuyao, Chekiang Province. A series of investigations and experiments were conducted in the year of 1955, in order to realize the variations of soil chemical properties and rice growth on those rotated paddy fields. The results obtained are summerized as follows.