Tower crane slewing bearings usually use small-sized four-point contact ball slewing bearings () or double-row ball slewing bearings (), with a diameter of  2 meters ~3 meters.

The slewing structure of the tower crane is divided into a lower slewing structure and an upper slewing structure.

The lower slewing tower crane sets the slewing bearing and the main structure of the balance weight at the bottom. Its advantages are: the tower type has less bending moment, low center of gravity, good stability, and convenient installation and maintenance. The disadvantage is that it has higher requirements for the slewing bearing. Height is restricted. The upper slewing tower crane sets the slewing support balance weight and the main mechanism on the top. Its advantage is that the lower structure of the tower body can be simplified because the tower body does not rotate, and it is convenient for jacking and adding joints. The disadvantage is that when the building exceeds the height of the tower body, due to the influence of the balance arm, the rotation of the tower crane is limited. At the same time, the center of gravity is high, the wind pressure increases, and the pressure weight increases, which increases the total weight of the whole machine.