A water supply system for a passive special safety system of a nuclear power plant, which is connected to a passive containment cooling system, a secondary-side passive cooling system, a spraying system and/or a reactor core assembly of the passive special safety system of the nuclear power plant, wherein: said water supply system comprises at least one steam-pressurizing water tank, at least one steam-pressurizing pipeline, at least one water replenishing pipeline and a drain pipeline; each steam-pressurizing water tank, in use, is connected to the steam generated by the steam generator and is pressurized by the steam to drive the water in the steam-pressurizing water tank to be delivered out; each steam-pressurizing pipeline is connected with a steam-pressurizing water tank and, in use, is connected to a steam generator in the passive special safety system of the nuclear power plant and/or an external steam system; each water replenishing pipeline is connected with a steam-pressurizing water tank and, in use, is connected to an external water source; the drain pipeline is connected to the steam-pressurizing water tanks and, in use, is connected to to the passive containment cooling system, the secondary-side passive cooling system, the spraying system, and/or the reactor core assembly, wherein each steam-pressurizing water tank comprises a tank body, a plurality of partition plates and a plurality of water chambers; characterized in that the tank body is a horizontal tank; the plurality of the partition plates are provided in the tank body and are arranged at intervals along the length direction of the tank body, partitioning a space in the tank body into a plurality of water chambers; the plurality of water chambers comprises a left water chamber and a right water chamber arranged along the length direction of the tank body; the upper part of the left water chamber of the tank body is provided with a pressurized steam inlet, connected to a steam-pressurizing pipeline; and the lower part of the right water chamber of the tank body is provided with a drain outlet, connected to the drain pipeline. said water supply system comprises at least one steam-pressurizing water tank, at least one steam-pressurizing pipeline, at least one water replenishing pipeline and a drain pipeline; each steam-pressurizing water tank, in use, is connected to the steam generated by the steam generator and is pressurized by the steam to drive the water in the steam-pressurizing water tank to be delivered out; each steam-pressurizing pipeline is connected with a steam-pressurizing water tank and, in use, is connected to a steam generator in the passive special safety system of the nuclear power plant and/or an external steam system; each water replenishing pipeline is connected with a steam-pressurizing water tank and, in use, is connected to an external water source; the drain pipeline is connected to the steam-pressurizing water tanks and, in use, is connected to to the passive containment cooling system, the secondary-side passive cooling system, the spraying system, and/or the reactor core assembly, wherein each steam-pressurizing water tank comprises a tank body, a plurality of partition plates and a plurality of water chambers; characterized in that the tank body is a horizontal tank; the plurality of the partition plates are provided in the tank body and are arranged at intervals along the length direction of the tank body, partitioning a space in the tank body into a plurality of water chambers; the plurality of water chambers comprises a left water chamber and a right water chamber arranged along the length direction of the tank body; the upper part of the left water chamber of the tank body is provided with a pressurized steam inlet, connected to a steam-pressurizing pipeline; and the lower part of the right water chamber of the tank body is provided with a drain outlet, connected to the drain pipeline.