The circular type caisson is one of the most widely used structures in the open sea of northern China. Several actual projects prove that the inner forces of bottom and side walls are mainly affected by the layout of the inner partition. Setting the diameter and external load and changing the layout of the inner partition, the analysis of the inner forces of the bottom slab and the side walls shows that more partitions are better for the bottom and worse for the side wall, and the radial-direction partition is better than other types of partitions. Layouts for the inner partition of different parts of the caisson, i.e. the upper part, the middle part and the lower part, are put forward.