The invention provides a field repairing method of welding cracks of a feeding slip-ring body of a large-sized slide mill, wherein a field detection step comprises the following steps of coloring, detecting defects, drilling crack arrest holes and cleaning and polishing a surface; a repairing welding step comprises reinforcing plate repairing welding, repairing welding method and defect re-detection; in a machine processing step, a supporting frame arranged near a feeding slip-ring body is used for installing a turning machine for grinding and processing the surface of the maximum outside diameter of a slip ring; and finally, the field repairing is achieved by replacing a new bearing bush and commissioning and inspecting a cylinder body. The invention utilizes an installation base of the traditional device without disassembling the cylinder body of the traditional large-sized slide mill and has short repairing period, simple operation and safe and reliable running. The field repairingmethod of the welding cracks of the feeding slip-ring body is also suitable for the field reparation of welding cracks of a discharging slip-ring cone.