Abstract: Cast iron is a very widely used material in the machinery industry, and casting defects often occur in the production.While the cast iron is one of difficult materials to weld.Five welding processes including manual arc welding, EDM surfacing, thermal welding (oxygen-acetylene welding), patch resistance welding and precision welding were used to repair nodular iron matrix casting.The macroscopic morphology, metallographic structure and mechanical properties of the repair welded joints were analyzed, which could provide a practical basis for the selection of welding repair process.