Abstract: The HIP combined cylinder structure of large nuclear power turbine units has the characteristics of large thermal capacity and slow cooling after shutdown.The article introduces various load reduction cooling schemes for HIP cylinder.A detailed quantitative analysis was conducted on the temperature, stress, and gap changes of the entire HIP module during the load reduction cooling process based on actual operating data of the power plant.Accelerating the cooling of the unit and shortening maintenance downtime while ensuring its safety has urgent practical significance and economic value.