Abstract: Due to its unique structure, the defects of gray cast iron are difficult to be repaired by welding, and cracks are easy to occur in the welding process, especially in the field welding of the cracked flange hole bridge.The welding deposited metal is easy to cause the bolt hole diameter to become small or to be blocked, so it is not possible to penetrate the bolt freely.Through the analysis of the cause of weld crack and the change of bolt hole diameter, the repair process by using nickel base welding material + welding buffer layer and pre-pluging the refractory material to the holes in welding repair area was put forward, which can meet the actual requirement.It solves all kinds of problems in repairing crack of gray cast iron flange hole bridge, and obtains good repairing effect.