According to the structural characteristics and welding requirements of a freight wheel hub-assembly,a Cartesian coordinates automatic spot-welding robotics is designed. It expounds the design,optimization and application of the sensor control system of automatic spot-welding robotics. The repetitive positioning accuracy of spot-welding robotics is verified by field process experiment and industrial experiment. The welding parameters of automatic spot-welding of wheel hub-disk are explored,which provides a reference method for automatic welding of freight wheel hub-assembly.