The invention relates to a circulating cooling water device applied to a petroleum driller braking system and an application method. The system comprises a water storing tank, a flow guide plate, a water supplementing loop, a water draining loop and a water returning loop, wherein a heat insulation board is arranged on the inner wall of the water storing tank, and the flow guide plate is arranged in the water storing tank; in case of pouring water into the water storing tank, a water source pipeline can be connected, and a seventh valve can be opened; if a pump A is used for supplying water, a third valve and a fourth valve are opened; if a pump B is used for supplying water, a fifth valve and a sixth valve are opened, a water source valve is opened, and the rest valves are closed; after a water pump is subjected to air exhausting, the pump A or the pump B is started, and a twelfth valve is gradually opened; when the water pouring is finished, the twelfth valve is closed, then the pump A or the pump B is stopped, and the rest opened valves are closed. The circulating cooling water device is low in manufacturing cost; a water storing part is manufactured from common steel and heat insulation material; the circulating water storing tank is free of extra heating in winter, so that the energy consumption can be saved; the water pump and a cooler are reasonably assembled and used, so that the cooling efficiency of the circulating cooling water can be greatly improved.