The invention belongs to the technical field of internal combustion engines, and aims at providing a pressurized water reactor nuclear power station emergency diesel engine body crack repairing structure and method. The repairing structure comprises slotted hole sets and connecting pieces, the slotted hole sets passing through a crack are arranged on an engine body in a manner of extending in thedirection vertical to the crack, wave keys are inlaid into the slotted hole sets, in the manner, the mechanical connecting manner is used for quickly and conveniently tightening the crack, expansion of the crack is limited, and the engine body strength loss generated after cracking is supplemented in time; and when the extension strength needed by the engine body is large, at least one row of slotted hole sets is arranged, a plurality of sealing holes are formed in the two sides of each slotted hole set along the crack, sealing screw pieces are inserted into corresponding sealing holes and aremade to abut against each other, the crack is accordingly sealed, and stress concentration on the crack face is eliminated. The repairing structure and the corresponding repairing method solve the technical problem that crack defects of a diesel engine block are difficult to repair through repair welding, the structure is simple and reliable, and crack repairing is convenient, quick and better ineffect.