Turntable bearing is a kind of large bearing with special structure which can bear the comprehensive loads such as axial load, radial load and overturning moment at the same time. Generally speaking, the turntable bearing is equipped with installation hole, lubricating oil and sealing device which can meet the different requirements of all kinds of main engines under different working conditions. On the other hand, the turntable bearing has the characteristics of compact structure, easy to guide rotation, easy to install and easy to maintain, etc. The turntable bearing is widely used in large rotary devices such as hoisting and transportation machinery, excavators, construction engineering machinery, port machinery, wind power generation, medical equipment, radar and missile launcher.