The Double-Row Ball type Slewing Ring has three races. The steel ball and the spacer block can be directly discharged into the upper and lower raceways. According to the force condition, two rows of steel balls with different diameters are arranged. This open assembly is very convenient, the upper and lower circular races have a bearing angle of 90° and can withstand large axial forces and tipping moments. When the radial force is greater than 0.1 times the axial force, the raceway must be specially designed. The double-row and different-diameter spherical slewing bearings have relatively large axial and radial dimensions and are structurally fastened. This kind of heavy slewing drive is especially suitable for loading and unloading machines such as tower cranes and truck cranes that require medium and large diameters.