Arrangement method of reactor building, reactor building and cooling method of reactor building

The invention discloses an arrangement method of a reactor building, the reactor building and a cooling method of the reactor building, which can ensure that other parts of main equipment of a reactor can still be arranged in the reactor under the conditions that the capacity of a safe built-in water tank is set to be large and the total size of a containment does not need to be increased, so that the construction cost of the reactor can be reduced, and the construction efficiency is improved. The economical efficiency is improved. The method comprises the following steps that the interior of a containment (2) is divided into N layers of spaces from bottom to top, and N is a positive integer and is larger than or equal to 2; arranging reactor pressure vessels (4) in the reactor main equipment in the reactor pit (3), and enabling the reactor pressure vessels (4) to be positioned on a first layer at the bottommost part of the multilayer space and a plurality of layers above the first layer; a safe built-in wate