A cooling system for a blast furnace includes a cooling circuit (10) closed by a return line (16) and at least one circulation pump (26, 26′, 26″) for circulating cooling water through the closed cooling circuit. An emergency feed line (36) with an emergency feed valve (38), which opens in case of a power failure, is connected to the cooling circuit (10). An emergency overflow valve (68) is located at the highest point of the closed cooling circuit (10). This emergency overflow valve (68) opens in case of a power failure, so that the closed cooling circuit (10) becomes an open cooling circuit (10) with an atmospheric pressure discharge at its highest point. A pressure vessel (34), which is connected to the emergency feed line (36), contains a certain volume of emergency water which is pressurised by a gas, so that, in case of a power failure, an emergency water flow establishes through the open cooling circuit (10).