External steam cooling ware water supply system of low capacity, it includes that one disposes at the external steam cooling ware of the low capacity of thermal power plant, the external steam cooling ware of low capacity has concatenated big orifice plate of the person in charge and steam cooling ware supply line through importing and exporting water feeding pipe, external steam cooling ware import and export and to have set up water of the same kind side feedwater bypass pipeline, a bypass aperture plate of installation and a bypass electric brake valve on feedwater bypass pipeline between the water feeding pipe, the external steam cooling ware of low capacity arrange in the main supply line of steam turbine room distance at a distance, by feedwater bypass piped water supply, it has simple structure, uses simple to operate, has both guaranteed external steam cooling ware operation safety, can improve external steam cooling ware again and arrange the position flexibility to reduce the investment, compression main building size reduces the transformation unit and increases characteristics such as external steam cooling ware difficulty.