Single-row four-point contact ball slewing bearing is divided into external gear, internal gear and non-gear. Its structure is composed of two seat-rings. There is a row of steel balls as rolling body, and there is a single separator among steel balls. Inner and outer rings are whole styles, and filled with balls though filling holes. This kind of slewing bearing is of compact structure, light weight, four-point contact between steel balls and raceways. It can bear normal force, radial force and tilting moment at the same time, with a great loading capability. It is used in turntable conveyor, welding operator, medium-small type crane and excavator and other engineering machinery.