The invention discloses a nuclear island evaporator sleeve part hole forming method. The nuclear island evaporator sleeve part hole forming method comprises the steps of (1), steel ingot heating; (2),forging stock blanking; (3), forging stock upsetting and pulling; (4), primary punching; (5), secondary punching, specifically, a demoulding expanding agent is filled into the inner cavity of a punching head, and the demoulding expanding agent makes contact with the high temperature forging part hole bottom to be expanded to push the punching head out of a hole; (6), three-time punching, specifically, the demoulding expanding agent is filled into the inner cavity of the punching head again, and the punching head is pushed out after expanding; (7), four-time punching, specifically, the demoulding expanding agent is further filled into the inner cavity of the punching head, and the punching head is pushed out after expanding; (8), hole trimming; (9), heat treating after forging. The demoulding expanding agent comprises the ingredients of, in percentage by mass, 8-12% of tung oil, 20-25% of saw powder, 10-15% of graphite, 3-5% of water and the balance blind coal, and the filling amount of the demoulding expanding agent at a time is 200-500g. By means of the nuclear island evaporator sleeve part hole forming method, longhole punching performed on nuclear forging parts is realized, andthe nuclear island evaporator sleeve part hole forming method has the advantages that the demoulding speed is fast, the tissue of the forging parts is uniform and dense, and the material utilizationrate is high.